AEROPLANES 


WITH  ORIGINAL  ILLUSTRATIONS 


AEROPLANES 


AEROPLANES 


BY 

J.  S.  ZERBE,  M.E. 


Author  of 
Automobiles — Motors 


ILLUSTRATED 


NEW  YORK 
CUPPLES  &  LEON  COMPANY 


COPYRIGHT,  1915,  BY 
CUPPLES  &  LEON  COMPANY 


LIBRARY 

UNIVERSITY  OF  CALIFORNIA 
SANTA  BARBARA 


CONTENTS 

PAGE 

INTRODUCTORY 1-3 

CHAPTER  I.    THEORIES  A^ND  FACTS  ABOUT  FLYING     .     .      5-32 

The  "Science"  of  Aviation.  Machine  Types.  Shape 
or  Form  not  Essential.  A  Stone  as  a  Flying  Machine. 
Power  the  Great  Element.  Gravity  as  Power.  Mass 
and  Element  in  Flying.  Momentum  a  Factor.  Resist- 
ance. How  Resistance  Affects  Shape.  Mass  and  Re- 
sistance. The  Early  Tendency  to  Eliminate  Momen- 
tum. Light  Machines  Unstable.  The  Application  of 
Power.  The  Supporting  Surfaces.  Area  not  the  Es- 
sential Thing.  The  Law  of  Gravity.  Gravity.  Inde- 
structibility of  Gravitation.  Distance  Reduces  Gravi- 
tational Pull.  How  Motion  Antagonizes  Gravity.  A 
Tangent.  Tangential  Motion  Represents  Centrifugal 
Pull.  Equalizing  the  Two  Motions.  Lift  and  Drift. 
Normal  Pressure.  Head  Resistance.  Measuring  Lift 
and  Drift.  Pressure  at  Different  Angles.  Difference 
Between  Lift  and  Drift  in  Motion.  Tables  of  Lift  and 
Drift.  Why  Tables  of  Lift  and  Drift  are  Wrong. 
Langley's  Law.  Moving  Planes  vs.  Winds.  Momen- 
tum not  Considered.  The  Flight  of  Birds.  The 
Downward  Beat.  The  Concaved  Wing.  Feather  Struc- 
ture Considered.  Webbed  Wings.  The  Angle  of  Move- 
ment. An  Initial  Movement  or  Impulse  Necessary.  A 
Wedging  Motion.  No  Mystery  in  the  Wave  Motion. 
How  Birds  Poise  with  Flapping  Wings.  Narrow- 
winged  Birds.  Initial  Movement  of  Soaring  Birds. 
Soaring  Birds  Move  Swiftly.  Muscular  Energy  Ex- 
erted by  Soaring  Birds.  Wings  not  Motionless. 

CHAPTER  II.    PRINCIPLES  OF  AEROPLANE  FLIGHT  .     .     .     33-39 

Speed  as  one  of  the  Elements.  Shape  and  Speed. 
What  "Square  of  the  Speed"  Means.  Action  of  a 
"Skipper."  Angle  of  Incidence.  Speed  and  Surface. 
Control  of  the  Direction  of  Flight.  Vertical  Planes. 

CHAPTER  III.    THE  FORM  OR  SHAPE  OF  FLYING  MACHINES    40-49 

The  Theory  of  Copying  Nature.  Hulls  of  Vessel^. 
Man  Does  not  Copy  Nature.  Principles  Essential,  not 
Forms.  Nature  not  the  Guide  as  to  Forms.  The  Pro- 
peller Type.  Why  Specially-designed  Forms  Improve 


CONTENTS 

PAGE 

Natural  Structures.  Mechanism  Devoid  of  Intelli- 
gence. A  Machine  Must  Have  a  Substitute  for  In- 
telligence. Study  of  Bird  Flight  Useless.  Shape  of 
Supporting  Surface.  The  Trouble  Arising  From  Out- 
stretched Wings.  Density  of  the  Atmosphere.  Elas- 
ticity of  the  Air.  "Air  Holes."  Responsibility  for 
Accidents.  The  Turning  Movement.  Centrifugal  Ac- 
tion. The  Warping  Planes. 

CHAPTEB  IV.    FOBE  AND  AFT  CONTBOL 50-64 

The  Bird  Type  of  Fore  and  Aft  Control.  Angle  and 
Direction  of  Flight.  Why  Should  the  Angle  of  the 
Body  Change.  Changing  Angle  of  Body  not  Safe.  A 
Non-changing  Body.  Descending  Positions  by  Power 
Control.  Cutting  off  the  Power.  The  Starting  Move- 
ment. The  Suggested  Type.  The  Low  Center  of  Grav- 
ity. Fore  and  Aft  Oscillations.  Application  of  the 
New  Principle.  Low  Weight  not  Necessary  with  Syn- 
chronously-moving Wings. 

CHAPTEB  V.    DIFFEBENT    MACHINE    TYPES    AND    THEIB 

CHABACTEBISTICS 65-73 

The  Helicopter.  Aeroplanes.  The  Monoplane.  Its 
Advantages.  Its  Disadvantages.  The  Bi-plane.  Sta- 
bility in  Bi-planes.  The  Orthopter.  Nature's  Type 
not  Uniform.  Theories  About  Flight  of  Birds.  In- 
stinct. The  Mode  of  Motion.  The  Wing  Structure. 
The  Wing  Movement.  The  Helicopter  Motion. 

CHAPTEB  VI.    THE  LIFTING  SUBFACES  OF  AEROPLANES   .     74-84 

Relative  Speed  and  Angle.  Narrow  Planes  Most  Ef- 
fective. Stream  Lines  Along  a  Plane.  The  Center  of 
Pressure.  Air  Lines  on  the  Upper  Side  of  a  Plane. 
Rarefied  Area.  Rarefaction  Produced  by  Motion.  The 
Concaved  Plane.  The  Center  of  Pressure.  Utilizing 
the  Rarefied  Area.  Changing  Center  of  Pressure. 
Plane  Monstrosities.  The  Bird  Wing  Structure. 
Torsion.  The  Bat's  Wing.  An  Abnormal  Shape.  The 
Tail  as  a  Monitor. 

CHAPTEB  VII.    ABNOBMAL  FLYING  STUNTS  AND  SPEEDS  .     85-93 

Lack  of  Improvements  in  Machines.  Men  Exploited 
and  not  Machines.  Abnormal  Flying  of  no  Value. 
The  Art  of  Juggling.  Practical  Uses  the  Best  Test. 
Concaved  and  Convex  Planes.  How  Momentum  is  a 
Factor  in  Inverted  Flying.  The  Turning  Movement. 
When  Concaved  Planes  are  Desirable.  The  Speed 
Mania.  Uses  of  Flying  Machines.  Perfection  in  Ma- 
chines Must  Come  Before  Speed.  The  Range  of  its 
Uses.  Commercial  Utility. 


CONTENTS 

PAGE 

CHAPTEB  VIII.    KITES  AND  GLIDEBS 94-112 

The  Dragon  Kite.  Its  Construction.  The  Malay 
Kite.  Dihedral  Angle.  The  Common  Kite.  The  Bow 
Kite.  The  Box  Kite.  The  Voison  Bi-plane.  Lateral 
Stability  in  Kites,  not  Conclusive  as  to  Planes.  The 
Spear  Kite.  The  Cellular  Kite.  Tetrahedral  Kite. 
The  Deltoid.  The  Dunne  Flying  Machine.  Rotating 
Kite.  Kite  Principles.  Lateral  Stability  in  Kites. 
Similarity  of  Fore  and  Aft  Control.  Gliding  Flight. 
One  of  the  Uses  of  Glider  Experiments.  Hints  in 
Gliding. 

CHAPTEB  IX.    AEBOPLANE  CONSTBUCTION     ....       113-130 

Lateral  and  Fore  and  Aft.  Transverse.  Stability 
and  Stabilization.  The  Wright  System.  Controlling 
the  Warping  Ends.  The  Curtiss  Wings.  The  Farman 
Ailerons.  Features  Well  Developed.  Depressing  the 
Eear  End.  Determining  the  Size.  Rule  for  Placing 
the  Planes.  Elevating  Plane.  Action  in  Alighting. 
The  Monoplane.  The  Common  Fly.  Stream  Lines. 
The  Monoplane  Form. 

CHAPTEB  X.    POWEB  AND  ITS  APPLICATION  ....      131-142 

Features  in  Power  Application.  Amount  of  Power 
Necessary.  The  Pull  of  the  Propeller.  Foot  Pounds. 
Small  Amount  of  Power  Available.  High  Propeller 
Speed  Important.  Width  and  Pitch  of  Blades.  Effect 
of  Increasing  Propeller  Pull.  Disposition  of  the 
Planes.  Different  Speeds  with  Same  Power.  Increase 
of  Speed  Adds  to  Resistance.  How  Power  Decreases 
with  Speed.  How  to  Calculate  the  Power  Applied. 
Pulling  Against  an  Angle.  The  Horizontal  and  the 
Vertical  Pull.  The  Power  Mounting.  Securing  the 
Propeller  to  the  Shaft.  Vibrations.  Weaknesses  in 
Mounting.  The  Gasoline  Tank.  Where  to  Locate  the 
Tank.  The  Danger  to  the  Pilot.  The  Closed-in  Body. 
Starting  the  Machine.  Propellers  with  Varying  Pitch. 

CHAPTEB  XI.    FLYING  MACHINE  ACCESSOBIES  .     .     .       143-166 

The  Anemometer.  The  Anemograph.  The  Anemo- 
metrograph.  The  Speed  Indicator.  Air  Pressure  In- 
dicator. Determining  the  Pressure  From  the  Speed. 
Calculating  Pressure  From  Speed.  How  the  Figures 
are  Determined.  Converting  Hours  Into  Minutes. 
Changing  Speed  Hours  to  Seconds.  Pressure  as  the 
Square  of  the  Speed.  Gyroscopic  Balance.  The  Prin- 
ciples Involved.  The  Application  of  the  Gyroscope. 
Fore  and  Aft  Gyroscopic  Control.  Angle  Indicator. 
Pendulum  Stabilizer.  Steering  and  Controlling 


CONTENTS 

PAGE 

Wheel.  Automatic  Stabilizing  Wings.  Barometers. 
Aneroid  Barometer.  Hydroplanes.  Sustaining  Weight 
of  Pontoons.  Shape  of  the  Pontoon. 

CHAPTEB  XII.    EXPERIMENTAL  WOBK'IN  FLYING  .     .       167-185 

Certain  Conditions  in  Flying.  Heat  in  Air.  Motion 
When  in  Flight.  Changing  Atmosphere.  "Ascending 
Currents."  "Aspirate  Currents."  Outstretched  Wings. 
The  Starting  Point.  The  Vital  Part  of  the  Machine. 
Studying  the  Action  of  the  Machine.  Elevating  the 
Machine.  How  to  Practice.  The  First  Stage.  Pa- 
tience the  Most  Difficult  Thing.  The  Second  Stage. 
The  Third  Stage.  Observations  While  in  Flight.  Fly- 
ing in  a  Wind.  First  Trials  in  a  Quiet  Atmosphere. 
Making  Turns.  The  Fourth  Stage.  The  Figure  8. 
The  Vol  Plane.  The  Landing.  Flying  Altitudes. 

CHAPTEB  XIII.    THE  PROPELLER 186-195 

Propeller  Changes.  Propeller  Shape.  The  Diameter. 
Pitch.  Laying  Out  the  Pitch.  Pitch  Kule.  Lami- 
nated Construction.  Laying  up  a  Propeller  Form. 
Making  Wide  Blades.  Propeller  Outline.  For  High 
Speeds.  Increasing  Propeller  Efficiency. 

CHAPTER  XIV.    EXPERIMENTAL  GLIDEBS  AND  MODEL  AEBO- 

PLANES i  •     •       196-205 

The  Relation  of  Models  to  Flying  Machines.  Les- 
sons From  Models.  Flying  Model  Aeroplanes.  An 
Efficient  Glider.  The  Deltoid  Formation.  Racing 
Models.  The  Power  for  Model  Aeroplanes.  Making 
the  Propeller.  Material  for  the  Propeller.  Rubber. 
Propeller  Shape  and  Size.  Supporting  Surfaces. 

CHAPTEB  XV.    THE  AEROPLANE  IN  THE  GREAT  WAB  .       206-222 

Balloon  Observations.  Changed  Conditions  in  WTar- 
fare.  The  Effort  to  Conceal  Combatants.  Smokeless 
Powder.  Inventions  to  Attack  Aerial  Craft.  Func- 
tions of  the  Aeroplane  in  War.  Bomb-throwing  Tests. 
Method  for  Determining  the  Movement  of  a  Bomb. 
The  Great  Extent  of  Modern  Battle  Lines.  The  Aero- 
plane Detecting  the  Movements  of  Armies.  The  Ef- 
fective Height  for  Scouting.  Sizes  of  Objects  at  Great 
Distances.  Some  Daring  Feats  in  War.  The  German 
Taube.  How  Aeroplanes  Report  Observations.  Sig- 
nal Flags.  How  Used.  Casualties  Due  to  Bombs 
From  Aeroplanes. 

GLOSSARY ,  .     223-242 


LIST  OF  ILLUSTRATIONS 

FIG.  PAGE 

1.  Tangential   flight    16 

2.  Horizontal ,  flight    18 

3.  Lift  and  drift   10 

4.  Normal    air    pressure    20 

5.  Edge    resistance    20 

6.  Measuring  lift  and  drift 21 

7.  Equal  lift  and  drift  in  flight 25 

8.  Unequal  lift  and  drift  25 

9.  Wing   movement    in    flight    29 

10.  Evolution  of  humming-bird's  wing 30 

11.  A  skipper  in  flight  35 

1  la.  Monoplane  in  flight  52 

12.  Angles   of   flight    53 

13.  Planes  on  non-changing  body    55 

14.  Descent  with  non-changing  body    56 

15.  Utilizing  momentum    57 

16.  Reversing   motion     58 

17.  Showing  changing  angle  of  body   59 

18.  Showing  non-changing   angle   of   frame    60 

19.  Normal  flight,  with  propeller  pulling   61 

20.  Action  when  propeller  ceases  to  pull 62 

21.  Synchronously-moving   planes    63 

22.  Stream  lines  along  a  plane   75 

23.  Air  lines  on  the  upper  side  of  a  plane 78 

24.  Air  lines  below  a  concaved  plane  79 

25.  Air  lines  above  a  convex  plane    80 

26.  Changing  centers  of  pressures    81 

27.  Changing  centers  of  pressures    81 

28.  Bird-wing    structures     81 

29.  Bird-wing    structures    81 


LIST  OF  ILLUSTRATIONS 

FIG.  PAGE 

30.  One  of  the  monstrosities   83 

31.  Flying  upside  down   89 

32.  Chart  showing  range  of  uses   92 

33.  Ribs   of    dragon   kite    95 

34.  The    Malay    kite     96 

35.  Dihedral   angle    96 

36.  Common    kite    97 

37.  Bow   kite    98 

38.  Sexagonal   kite    98 

39.  Hargreave  kite    99 

40.  Voison   biplane    100 

41.  Spear  kite    101 

42.  Cellular  kite    101 

43.  Tetrahedral  kite    102 

44.  Deltoid   formation    103 

45.  Deltoid    formation    103 

46.  The  Dunne  bi-plane   104 

47.  Rotable  umbrella  kite   105 

48.  Action  of  wind  forces  on  kite   107 

49.  Farman    ailerons    115 

49a.  Rule  for  spacing  planes    119 

50.  Frame  of  control  planes   119 

51.  Side  elevation   of   frame    120 

52.  Frame  with  running  gear    120 

53.  Plan    view    122 

54.  Alighting     123 

55.  Common  fly.     Outstretched  wings 125 

56.  Common  fly.     Folded  wings    126 

57.  Relative  size  of  wing  and  body   126 

58.  Plan  of  monoplane    128 

59.  Side  elevation,  monoplane   129 

60.  Horizontal  and  vertical  pull  137 

61.  Speed  indicator 144 

62.  Air  pressure  indicator    145 

63.  The  gyroscope   151 

64.  Application  of  the  gyroscope    152 

65.  Action  of  the  gyroscope   153 

66.  Angle    indicator    .155 


LIST  OF  ILLUSTRATIONS 

FIG.  PAGE 

67.  Simple    pendulum    stabilizer 156 

68.  Pendulum  stabilizers   157 

69.  Steering  and   control  wheel    158 

70.  Automatic   stabilizing   wings    159 

71.  Action  of  stabilizing  wings  159 

72.  Into  the  wind  at  an  angle   160 

73.  Turning  a  circle   161 

74.  Aneroid    barometer    162 

75.  Hydroplane    floats    165 

76.  Describing  the  pitch  line   188 

77.  Laying  out  the  pitch    189 

78.  A  laminated  blank 191 

79.  Arranging  the   strips    192 

80.  End  view  of  blank    192 

81.  Marking  the  side   193 

82.  Outlining    193 

83.  Cut  from  a  4"  x  6"  single  blank   194 

84.  A   suggested   form 195 

85.  Deltoid  glider 199 

86.  The  Deltoid  racer   199 

87.  "A"  shaped  racing  glider   201 

88.  Making  the   propeller 203 

89.  Shape  and  size    205 

90.  Course  of  a  bomb   210 

91.  Determining  altitude  and  speed  211 


INTEODUCTOEY 

In  preparing  this  volume  on  Flying  Machines 
the  aim  has  been  to  present  the  subject  in  such  a 
manner  as  will  appeal  to  boys,  or  beginners,  in 
this  field  of  human  activity. 

The  art  of  aviation  is  in  a  most  primitive  state. 
So  many  curious  theories  have  been  brought  out 
that,  while  they  furnish  food  for  thought,  do  not, 
in  any  way,  advance  or  improve  the  structure  of 
the  machine  itself,  nor  are  they  of  any  service 
in  teaching  the  novice  how  to  fly. 

The  author  considers  it  of  far  more  importance 
to  teach  right  principles,  and  correct  reasoning 
than  to  furnish  complete  diagrams  of  the  details 
of  a  machine.  The  former  teach  the  art,  whereas 
the  latter  merely  point  out  the  mechanical  ar- 
rangements, independently  of  the  reasons  for 
making  the  structures  in  that  particular  way. 

Eelating  the  history  of  an  art,  while  it  may  be 
interesting  reading,  does  not  even  lay  the  founda- 
tions of  a  knowledge  of  the  subject,  hence  that 
field  has  been  left  to  others. 

The  boy  is  naturally  inquisitive,  and  he  is  in- 
terested in  knowing  why  certain  things  are  neces- 
i 


2  INTRODUCTORY 

sary,  and  the  reasons  for  making  structures  in 
particular  ways.  That  is  the  void  into  which 
these  pages  are  placed. 

The  author  knows  from  practical  experience, 
while  experimenting  with  and  building  aeroplanes, 
how  eagerly  every  boy  inquires  into  details. 
They  want  the  reasons  for  things. 

One  such  instance  is  related  to  evidence  this 
spirit  of  inquiry.  Some  boys  were  discussing  the 
curved  plane  structure.  One  of  them  ventured 
the  opinion  that  birds '  wings  were  concaved  on  the 
lower  side.  "But,"  retorted  another,  "why  are 
birds'  wings  hollowed?" 

This  was  going  back  to  first  principles  at  one 
leap.  It  was  not  satisfying  enough  to  know  that 
man  was  copying  nature.  It  was  more  important 
to  know  why  nature  originated  that  type  of  for- 
mation, because,  it  is  obvious,  that  if  such  struc- 
tures are  universal  in  the  kingdom  of  flying  crea- 
tures, there  must  be  some  underlying  principle 
which  accounted  for  it. 

It  is  not  the  aim  of  the  book  to  teach  the  art 
of  flying,  but  rather  to  show  how  and  why  the 
present  machines  fly.  The  making  and  the  using 
are  separate  and  independent  functions,  and  of 
the  two  the  more  important  is  the  knowledge  how 
to  make  a  correct  machine. 

Hundreds  of  workmen  may  contribute  to  the 


INTRODUCTORY  3 

building  of  a  locomotive,  but  one  man,  not  a 
builder,  knows  better  how  to  handle  it.  To 
manipulate  a  flying  machine  is  more  difficult  to 
navigate  than  such  a  ponderous  machine,  because 
it  requires  peculiar  talents,  and  the  building  is 
still  more  important  and  complicated,  and  re- 
quires the  exercise  of  a  kind  of  skill  not  necessary 
in  the  locomotive. 

The  art  is  still  very  young;  so  much  is  done 
which  arises  from  speculation  and  theories;  too 
much  dependence  is  placed  on  the  aviator;  the 
desire  in  the  present  condition  of  the  art  is  to  ex- 
ploit the  man  and  not  the  machine ;  dare-devil  ex- 
hibitions seem  to  be  more  important  than  perfect- 
ing the  mechanism;  and  such  useless  attempts  as 
flying  upside  down,  looping  the  loop,  and  charac- 
teristic displays  of  that  kind,  are  of  no  value  to 
the  art. 

THE  AUTHOR. 


AEROPLANES 

CHAPTER  I 

THEOBIES  AND   FACTS   ABOUT   FLYING 

THE  "SCIENCE"  OF  AVIATION. — It  may  be 
doubted  whether  there  is  such  a  thing  as  a  "  sci- 
ence of  aviation."  Since  Langley,  on  May  6, 
1896,  flew  a  motor-propelled  tandem  monoplane 
for  a  minute  and  an  half,  without  a  pilot,  and  the 
Wright  Brothers  in  1903  succeeded  in  flying  a 
bi-plane  with  a  pilot  aboard,  the  universal  opin- 
ion has  been,  that  flying  machines,  to  be  success- 
ful, must  follow  the  structural  form  of  birds,  and 
that  shape  has  everything  to  do  with  flying. 

We  may  be  able  to  learn  something  by  care- 
fully examining  the  different  views  presented  by 
those  interested  in  the  art,  and  then  see  how  they 
conform  to  the  facts  as  brought  out  by  the  actual 
experiments. 

MACHINE  TYPES. — There  is  really  but  one  type 
of  plane  machine.  While  technically  two  forms 
are  known,  namely,  the  monoplane  and  the  bi- 

5 


6  AEROPLANES 

plane,  they  are  both  dependent  on  outstretched 
wings,  longer  transversely  than  fore  and  aft,  so 
far  as  the  supporting  surfaces  are  concerned,  and 
with  the  main  weight  high  in  the  structure,  thus, 
in  every  particular,  conforming  to  the  form 
pointed  out  by  nature  as  the  apparently  correct 
type  of  a  flying  structure. 

SHAPE  OB  FOBM  NOT  ESSENTIAL. — It  may  be 
stated  with  perfect  confidence,  that  shape  or  form 
has  nothing  to  do  with  the  mere  act  of  flying.  It 
is  simply  a  question  of  power.  This  is  a  broad 
assertion,  and  its  meaning  may  be  better  under- 
stood by  examining  the  question  of  flight  in  a 
broad  sense. 

A  STONE  AS  A  FLYING  MACHINE. — When  a  stone 
is  propelled  through  space,  shape  is  of  no  impor- 
tance. If  it  has  rough  and  jagged  sides  its  speed 
or  its  distance  may  be  limited,  as  compared  with 
a  perfectly  rounded  form.  It  may  be  made  in 
such  a  shape  as  will  offer  less  resistance  to  the  air 
in  flight,  but  its  actual  propulsion  through  space 
does  not  depend  on  how  it  is  made,  but  on  the 
power  which  propelled  it,  and  such  a  missile  is  a 
true  heavier-than-air  machine. 

A  flying  object  of  this  kind  may  be  so  con- 
structed that  it  will  go  a  greater  distance,  or  re- 
quire less  power,  or  maintain  itself  in  space  at 
less  speed ;  but  it  is  a  flying  machine,  nevertheless, 


THEORIES  AND  FACTS  7 

in  the  sense  that  it  moves  horizontally  through  the 
air. 

POWEE  THE  GREAT  ELEMENT. — Now,  let  us  ex- 
amine the  question  of  this  power  which  is  able  to 
set  gravity  at  naught.  The  quality  called  energy 
resides  in  material  itself.  It  is  something  within 
matter,  and  does  not  come  from  without.  The 
power  derived  from  the  explosion  of  a  charge  of 
powder  comes  from  within  the  substance ;  and  so 
with  falling  water,  or  the  expansive  force  of 
steam. 

GRAVITY  AS  POWER. — Indeed,  the  very  act  of  the 
ball  gradually  moving  toward  the  earth,  by  the 
force  of  gravity,  is  an  illustration  of  a  power 
within  the  object  itself.  Long  'after  Galileo 
firmly  established  the  law  of  falling  bodies  it  be- 
gan to  dawn  on  scientists  that  weight  is  force. 
After  Newton  established  the  law  of  gravitation 
the  old  idea,  that  power  was  a  property  of  each 
body,  passed  away. 

In  its  stead  we  now  have  the  firmly  established 
view,  that  power  is  something  which  must  have 
at  least  two  parts,  or  consist  in  pairs,  or  two  ele- 
ments acting  together.  Thus,  a  stone  poised  on 
a  cliff,  while  it  exerts  no  power  which  can  loe 
utilized,  has,  nevertheless,  what  is  called  potential 
energy.  When  it  is  pushed  from  its  lodging  place 
kinetic  energy  is  developed.  In  both  cases, 


8          AEROPLANES 

gravity,  acting  in  conjunction  with  the  mass  of 
the  stone,  produced  power. 

So  in  the  case  of  gunpowder.  It  is  the  unity  of 
two  or  more  substances,  that  causes  the  expan- 
sion called  power.  The  heat  of  the  fuel  convert- 
ing water  into  steam,  is  another  illustration  of  the 
unity  of  two  or  more  elements,  which  are  neces- 
sary to  produce  energy. 

MASS  AN  ELEMENT  IN  FLYING. — The  boy  who 
reads  this  will  smile,  as  he  tells  us  that  the  power 
which  propelled  the  ball  through  the  air  came 
from  the  thrower  and  not  from  the  ball  itself. 
Let  us  examine  this  claim,  which  came  from  a  real 
boy,  and  is  another  illustration  how  acute  his  mind 
is  on  subjects  of  this  character. 

We  have  two  balls  the  same  diameter,  one  of 
iron  weighing  a  half  pound,  and  the  other  of  cot- 
ton weighing  a  half  ounce.  The  weight  of  one 
is,  therefore,  sixteen  times  greater  than  the  other. 

Suppose  these  two  balls  are  thrown  with  the  ex- 
penditure of  the  same  power.  What  will  be  the 
result?  The  iron  ball  will  go  much  farther,  or, 
if  projected  against  a  wall  will  strike  a  harder 
blow  than  the  cotton  ball. 

MOMENTUM  A  FACTOK. — Each  had  transferred 
to  it  a  motion.  The  initial  speed  was  the  same, 
and  the  power  set  up  equal  in  the  two.  Why  this 
difference?  The  answer  is,  that  it  is  in  the  ma- 


THEORIES  AND  FACTS  9 

terial  itself.  It  was  the  mass  or  density  which  ac- 
counted for  the  difference.  It  was  mass  multi- 
plied by  speed  which  gave  it  the  power,  called,  in 
this  case,  momentum. 

The  iron  ball  weighing  eight  ounces,  multiplied 
by  the  assumed  speed  of  50  feet  per  second,  equals 
400  units  of  work.  The  cotton  ball,  weighing  y2 
ounce,  with  the  same  initial  speed,  represents  25 
units  of  work.  The  term  "unit  of  work"  means 
a  measurement,  or  a  factor  which  may  be  used  to 
measure  force. 

It  will  thus  be  seen  that  it  was  not  the  thrower 
which  gave  the  power,  but  the  article  itself.  A 
feather  ball  thrown  under  the  same  conditions, 
would  produce  a  half  unit  of  work,  and  the  iron 
ball,  therefore,  produced  800  times  more  energy. 

RESISTANCE. — Now,  in  the  movement  of  any  body 
through  space,  it  meets  with  an  enemy  at  every 
step,  and  that  is  air  resistance.  This  is  much 
more  effective  against  the  cotton  than  the  iron 
ball:  or,  it  might  be  expressed  in  another  way: 
The  momentum,  or  the  power,  residing  in  the 
metal  ball,  is  so  much  greater  than  that  within  the 
cotton  ball  that  it  travels  farther,  or  strikes  a 
more  effective  blow  on  impact  with  the  wall. 

How  RESISTANCE  AFFECTS  THE  SHAPE. — It  is  be- 
cause of  this  counterforce,  resistance,  that  shape 
becomes  important  in  a  flying  object.  The  metal 


10  AEROPLANES 

ball  may  be  flattened  out  into  a  thin  disk,  and  now, 
when  the  same-  force  is  applied,  to  project  it  for- 
wardly,  it  will  go  as  much  farther  as  the  differ- 
ence in  the  air  impact  against  the  two  forms. 

MASS  AND  RESISTANCE. — Owing  to  the  fact  that 
resistance  acts  with  such  a  retarding  force  on  an 
object  of  small  mass,  and  it  is  difficult  to  set  up  a 
rapid  motion  in  an  object  of  great  density,  light- 
ness in  flying  machine  structures  has  been  con- 
sidered, in  the  past,  the  principal  thing  neces- 
sary. 

THE  EAELY  TENDENCY  TO  ELIMINATE  MO- 
MENTUM.— Builders  of  flying  machines,  for  sev- 
eral years,  sought  to  eliminate  the  very  thing 
which  gives  energy  to  a  horizontally-movable 
body,  namely,  momentum. 

Instead  of  momentum,  something  had  to  be 
substituted.  This  was  found  in  so  arranging  the 
machine  that  its  weight,  or  a  portion  of  it,  would 
be  sustained  in  space  by  the  very  element  which 
seeks  to  retard  its  flight,  namely,  the  atmosphere. 

If  there  should  be  no  material  substance,  like 
air,  then  the  only  way  in  which  a  heavier-than-air 
machine  could  ever  fly,  would  be  by  propelling  it 
through  space,  like  the  ball  was  thrown,  or  by 
some  sort  of  impulse  or  reaction  mechanism  on 
the  air-ship  itself.  It  could  get  no  support  from 
the  atmosphere. 


THEOBIES  AND  FACTS  11 

LIGHT  MACHINES  UNSTABLE. — Gradually  the 
question  of  weight  is  solving  itself.  Aviators  are 
beginning  to  realize  that  momentum  is  a  wonder- 
ful property,  and  a  most  important  element  in 
flying.  The  safest  machines  are  those  which  have 
weight.  The  light,  willowy  machines  are  subject 
to  every  caprice  of  the  wind.  They  are  notori- 
ously unstable  in  flight,  and  are  dangerous  even 
in  the  hands  of  experts. 

THE  APPLICATION  OF  POWER. — The  thing  now  to 
consider  is  not  form,  or  shape,  or  the  distribu- 
tion of  the  supporting  surfaces,  but  how  to  apply 
the  power  so  that  it  will  rapidly  transfer  a  ma- 
chine at  rest  to  one  in  motion,  and  thereby  get 
the  proper  support  on  the  atmosphere  to  hold  it 
in  flight. 

THE  SUPPORTING  SURFACES. — This  brings  us  to 
the  consideration  of  one  of  the  first  great  prob- 
lems in  flying  machines,  namely,  the  supporting 
surfaces, — not  its  form,  shape  or  arrangement, 
(which  will  be  taken  up  in  their  proper  places),  but 
the  area,  the  dimensions,  and  the  angle  necessary 
for  flight. 

AREA  NOT  THE  ESSENTIAL  THING. — The  history 
of  flying  machines,  short  as  it  is,  furnishes  many 
examples  of  one  striking  fact:  That  area  has 
but  little  to  do  with  sustaining  an  aeroplane  when 
once  in  flight.  The  first  Wright  flyer  weighed 


12  AEROPLANES 

741  pounds,  had  about  400  square  feet  of  plane 
surface,  and  was  maintained  in  the  air  with  a  12 
horse  power  engine. 

True,  that  machine  was  shot  into  the  air  by  a 
catapult.  Motion  having  once  been  imparted  to  it, 
the  only  thing  necessary  for  the  motor  was  to 
maintain  the  speed. 

There  are  many  instances  to  show  that  when 
once  in  flight,  one  horse  power  will  sustain  over 
100  pounds,  and  each  square  foot  of  supporting 
surface  will  maintain  90  pounds  in  flight. 

THE  LAW  OF  GRAVITY. — As  the  effort  to  fly 
may  be  considered  in  the  light  of  a  struggle  to 
avoid  the  laws  of  nature  with  respect  to  matter, 
it  may  be  well  to  consider  this  great  force  as  a 
fitting  prelude  to  the  study  of  our  subject. 

Proper  understanding,  and  use  of  terms  is  very 
desirable,  so  that  we  must  not  confuse  them. 
Thus,  weight  and  mass  are  not  the  same.  Weight 
varies  with  the  latitude,  and  it  is  different  at  vari- 
ous altitudes ;  but  mass  is  always  the  same. 

If  projected  through  space,  a  certain  mass 
would  move  so  as  to  produce  momentum,  which 
would  be  equal  at  all  places  on  the  earth's  surface, 
or  at  any  altitude. 

Gravity  has  been  called  weight,  and  weight 
gravity.  The  real  difference  is  plain  if  gravity 
is  considered  as  the  attraction  of  mass  for  mass. 


THEOBIES  AND  FACTS  13 

Gravity  is  generally  known  and  considered  as  a 
force  which  seeks  to  draw  things  to  the  earth. 
This  is  too  narrow. 

Gravity  acts  in  all  directions.  Two  balls  sus- 
pended from  strings  and  hung  in  close  proximity 
to  each  other  will  mutually  attract  each  other. 
If  one  has  double  the  mass  it  will  have  twice  the 
attractive  power.  If  one  is  doubled  and  the  other 
tripled,  the  attraction  would  be  increased  six 
times.  But  if  the  distance  should  be  doubled  the 
attraction  would  be  reduced  to  one-fourth;  and 
if  the  distance  should  be  tripled  then  the  pull 
would  be  only  one-ninth. 

The  foregoing  is  the  substance  of  the  law, 
namely,  that  all  bodies  attract  all  other  bodies 
with  a  force  directly  in  proportion  to  their  mass, 
and  inversely  as  the  square  of  their  distance  from 
one  another. 

To  explain  this  we  cite  the  following  illustra- 
tion: Two  bodies,  each  having  a  mass  of  4 
pounds,  and  one  inch  apart,  are  attracted  toward 
each  other,  so  they  touch.  If  one  has  twice  the 
mass  of  the  other,  the  smaller  will  draw  the  larger 
only  one-quarter  of  an  inch,  and  the  large  one 
will  draw  the  other  three-quarters  of  an  inch, 
thus  confirming  the  law  that  two  bodies  will  at- 
tract each  other  in  proportion  to  their  mass. 

Suppose,  now,  that  these  balls  are  placed  two 


14  AEROPLANES 

inches  apart, — that  is,  twice  the  distance.  As 
each  is,  we  shall  say,  four  pounds  in  weight,  the 
square  of  each  would  be  16.  This  does  not  mean 
that  there  would  be  sixteen  times  the  attraction, 
but,  as  the  law  says,  inversely  as  the  square  of 
the  distance,  so  that  at  two  inches  there  is  only 
one-sixteenth  the  attraction  as  at  one  inch. 

If  the  cord  of  one  of  the  balls  should  be  cut,  it 
would  fall  to  the  earth,  for  the  reason  that  the 
attractive  force  of  the  great  mass  of  the  earth  is 
so  much  greater  than  the  force  of  attraction  in 
its  companion  ball. 

INDESTRUCTIBILITY  OF  GRAVITATION. — Gravity 
cannot  be  produced  or  destroyed.  It  acts  between 
all  parts  of  bodies  equally;  the  force  being  pro- 
portioned to  their  mass.  It  is  not  affected  by 
any  intervening  substance;  and  is  transmitted 
instantaneously,  whatever  the  distance  may  be. 

While,  therefore,  it  is  impossible  to  divest  mat- 
ter of  this  property,  there  are  two  conditions 
which  neutralize  its  effect.  The  first  of  these  is 
position.  Let  us  take  two  balls,  one  solid  and 
the  other  hollow,  but  of  the  same  mass,  or  density. 
If  the  cavity  of  the  one  is  large  enough  to  receive 
the  other,  it  is  obvious  that  while  gravity  is  still 
present  the  lines  of  attraction  being  equal  at 
all  points,  and  radially,  there  can  be  no  pull  which 
moves  them  together. 


*  THEOBIES  AND  FACTS  15 

DISTANCE  REDUCES  GRAVITATIONAL  PULL. — Or 
the  balls  may  be  such  distance  apart  that  the  at- 
tractive force  ceases.  At  the  center  of  the  earth 
an  object  would  not  weigh  anything.  A  pound 
of  iron  and  an  ounce  of  wood,  one  sixteen  times 
the  mass  of  the  other,  would  be  the  same, — abso- 
lutely without  weight. 

If  the  object  should  be  far  away  in  space  it 
would  not  be  influenced  by  the  earth's  gravity; 
so  it  will  be  understood  that  position  plays  an 
important  part  in  the  attraction  of  mass  for  mass. 

How  MOTION  ANTAGONIZES  GRAVITY. — The  sec- 
ond way  to  neutralize  gravity,  is  by  motion.  A 
ball  thrown  upwardly,  antagonizes  the  force  of 
gravity  during  the  period  of  its  ascent.  In  like 
manner,  when  an  object  is  projected  horizontally, 
while  its  mass  is  still  the  same,  its  weight  is  less. 

Motion  is  that  which  is  constantly  combating 
the  action  of  gravity.  A  body  moving  in  a  circle 
must  be  acted  upon  by  two  forces,  one  which  tends 
to  draw  it  inwardly,  and  the  other  which  seeks  to 
throw  it  outwardly. 

The  former  is  called  centripetal,  and  the  latter 
centrifugal  motion.  Gravity,  therefore,  repre- 
sents centripetal,  and  motion  centrifugal  force. 

If  the  rotative  speed  of  the  earth  should  be  re- 
tarded, all  objects  on  the  earth  would  be  increased 
in  weight,  and  if  the  motion  should  be  accelerated 


16 


AEROPLANES 


objects  would  become  lighter,  and  if  sufficient 
speed  should  be  attained  all  matter  would  fly  off 
the  surface,  just  as  dirt  flies  off  the  rim  of  a 
wheel  at  certain  speeds. 

A  TANGENT. — When  an  object  is  thrown  hori- 
zontally the  line  of  flight  is  tangential  to  the  earth, 


T^ig.  /  Thntienttal  T^ltgM. 

or  at  right  angles  to  the  force  of  gravity.  Such 
a  course  in  a  flying  machine  finds  less  resistance 
than  if  it  should  be  projected  upwardly,  or  di- 
rectly opposite  the  centripetal  pull. 

TANGENTIAL.  MOTION  REPRESENTS  CENTRIFUGAL 
PULL. — A    tangential    motion,    or    a    horizontal 


THEOBIES  AND  FACTS  17 

movement,  seeks  to  move  matter  away  from  the 
center  of  the  earth,  and  any  force  which  imparts 
a  horizontal  motion  to  an  object  exerts  a  centrifu- 
gal pull  for  that  reason. 

In  Fig.  1,  let  A  represent  the  surface  of  the 
earth,  B  the  starting  point  of  the  flight  of  an  ob- 
ject, and  C  the  line  of  flight.  That  represents  a 
tangential  line.  For  the  purpose  of  explaining 
the  phenomena  of  tangential  flight,  we  will  as- 
sume that  the- missile  was  projected  with  a  suf- 
ficient force  to  reach  the  vertical  point  D,  which 
is  4000  miles  from  the  starting  point  B. 

In  such  a  case  it  would  now  be  over  5500  miles 
from  the  center  of  the  earth,  and  the  centrifugal 
pull  would  be  decreased  to  such  an  extent  that  the 
ball  would  go  on  and  on  until  it  came  within  the 
sphere  of  influence  from  some  other  celestial 
body. 

EQUALIZING  THE  Two  MOTIONS. — But  now  let  us 
assume  that  the  line  of  flight  is  like  that  shown 
at  E,  in  Fig.  2,  where  it  travels  along  parallel 
with  the  surface  of  the  earth.  In  this  case  the 
force  of  the  ball  equals  the  centripetal  pull, — or, 
to  put  it  differently,  the  centrifugal  equals  the 
gravitational  pull. 

The  constant  tendency  of  the  ball  to  fly  off  at 
a  tangent,  and  the  equally  powerful  pull  of 
gravity  acting  against  each  other,  produce  a  mo- 


18  AEROPLANES 

tion  which  is  like  that  of  the  earth,  revolving 
around  the  sun  once  every  three  hundred  and 
sixty-five  days. 

It  is  a  curious  thing  that  neither  Langley,  nor 
any  of  the  scientists,  in  treating  of  the  matter  of 
flight,  have  taken  into  consideration  this  quality 


of  momentum,  in  their  calculations  of  the  ele- 
ments of  flight. 

All  have  treated  the  subject  as  though  the 
whole  problem  rested  on  the  angle  at  which  the 
planes  were  placed.  At  45  degrees  the  lift  and 
drift  are  assumed  to  be  equal. 


THEORIES  AND  FACTS 


19 


LIFT  AND  DRIFT. — The  terms  should  be  ex- 
plained, in  view  of  the  frequent  allusion  which 
will  be  made  to  the  terms  hereinafter.  Lift 
is  the  word  employed  to  indicate  the  amount 
which  a  plane  surface  will  support  while  in  flight. 
Drift  is  the  term  used  to  indicate  the  resistance 
which  is  offered  to  a  plane  moving  forwardly 
against  the  atmosphere. 


In  Fig.  3  the  plane  A  is  assumed  to  be  moving 
forwardly  in  the  direction  of  the  arrow  B.  This 
indicates  the  resistance.  The  vertical  arrow  C 
shows  the  direction  of  lift,  which  is  the  weight 
held  up  by  the  plane. 

NORMAL  PRESSURE. — Now  there  is  another  term 
much  used  which  needs  explanation,  and  that  is 
normal  pressure.  A  pressure  of  this  kind 
against  a  plane  is  where  the  wind  strikes  it  at 
right  angles.  This  is  illustrated  in  Fig.  4,  in 


20 


AEROPLANES 


which  the  plane  is  shown  with  the  wind  striking 
it  squarely. 

It  is  obvious  that  the  wind  will  exert  a  greater 
force  against  a  plane  when  at  its  normal.    On  the 


.  ^formal 


other  hand,  the  least  pressure  against  a  plane  is 
when  it  is  in  a  horizontal  position,  because  then 
the  wind  has  no  force  'against  the  surfaces,  and 
the  only  effect  on  the  drift  is  that  which  takes 
place  when  the  wind  strikes  its  forward  edge. 


HEAD  RESISTANCE. — Fig.  5  shows  such  a  plane, 
the  only  resistance  being  the  thickness  of  the 
plane  as  at  A.  This  is  called  head  resistance, 
and  on  this  subject  there  has  been  much  con- 
troversy, and  many  theories,  which  will  be  con- 
sidered under  the  proper  headings. 


THEORIES  AND  FACTS  21 

If  a  plane  is  placed  at  an  angle  of  45  degrees 
the  lift  and  the  drift  are  the  same,  assumedly,  be- 
cause, if  we  were  to  measure  the  power  required 
to  drive  it  forwardly,  it  would  be  found  to  equal 
the  weight  necessary  to  lift  it.  That  is,  suppose 
we  should  hold  a  plane  at  that  angle  with  a  heavy 
wind  blowing  against  it,  and  attach  two  pairs  of 
scales  to  the  plane,  both  would  show  the  same 
pull. 


MEASURING  LIFT  AND  DEIFT. — In  Fig.  6,  A  is  the 
plane,  B  the  horizontal  line  which  attaches  the 
plane  to  a  scale  C,  and  D  the  line  attaching  it  to 
the  scale  E.  When  the  wind  is  of  sufficient  force 
to  hold  up  the  plane,  the  scales  will  show  the  same 
pull,  neglecting,  of  course,  the  weight  of  the 
plane  itself. 

PRESSURE  AT  DIFFERENT  ANGLES. — What  every 
one  wants  to  know,  and  a  subject  on  which  a 


22  AEROPLANES 

great  deal  of  experiment  and  time  have  been  ex- 
pended, is  to  determine  what  the  pressures  are  at 
the  different  angles  between  the  horizontal,  and 
laws  have  been  formulated  which  enable  the  pres- 
sures to  be  calculated. 

DIFFERENCE    BETWEEN    LlFT    AND    DRIFT    IN    Mo- 

TION. — The  first  observation  is  directed  to  the  dif- 
ferences that  exist  between  the  lift  and  drift, 
when  the  plane  is  placed  at  an  angle  of  less  than 
45  degrees.  A  machine  weighing  1000  pounds 
has  always  the  same  lift.  Its  mass  does  not 
change.  Eemember,  now,  we  allude  to  its  mass, 
or  density. 

We  are  not  now  referring  to  weight,  because 
that  must  be  taken  into  consideration,  in  the 
problem.  As  heretofore  stated,  when  an  object 
moves  horizontally,  it  has  less  weight  than  when 
at  rest.  If  it  had  the  same  weight  it  would  not 
move  forwardly,  but  come  to  rest. 

When  in  motion,  therefore,  while  the  lift,  so 
far  as  its  mass  is  concerned,  does  not  change,  the 
drift  does  decrease,  or  the  forward  pull  is  less 
than  when  at  45  degrees,  and  the  decrease  is  less 
and  less  until  the  plane  assumes  a  horizontal  posi- 
tion, where  it  is  absolutely  nil,  if  we  do  not  con- 
sider head  resistance. 

TABLES  OF  LIFT  AND  DRIFT. — All  tables  of  Lift 
and  Drift  consider  only  the  air  pressures.  They 


THEOEIES  AND  FACTS  23 

do  not  take  into  account  the  fact  that  momentum 
takes  an  important  part  in  the  translation  of  an 
object,  like  a  flying  machine. 

A  mass  of  material,  weighing  1000  pounds  while 
at  rest,  sets  up  an  enormous  energy  when  moving 
through  the  air  at  fifty,  seventy-five,  or  one  hun- 
dred miles  an  hour.  At  the  latter  speed  the  move- 
ment is  about  160  feet  per  second,  a  motion  which 
is  nearly  sufficient  to  maintain  it  in  horizontal 
flight,  independently  of  any  plane  surface. 

Such  being  the  case,  why  take  into  account  only 
the  angle  of  the  plane?  It  is  no  wonder  that 
aviators  have  not  been  able  to  make  the  theoreti- 
cal considerations  and  the  practical  demonstra- 
tions agree. 

WHY  TABLES  or  LIFT  AND  DRIFT  ARE  WRONG. — 
A  little  reflection  will  show  why  such  tables  are 
wrong.  They  were  prepared  by  using  a  plane 
surface  at  rest,  and  forcing  a  blast  of  air  against 
the  plane  placed  at  different  angles;  and  for  de- 
termining air  pressures,  this  is,  no  doubt,  cor- 
rect. But  it  does  not  represent  actual  flying  con- 
ditions. It  does  not  show  the  conditions  existing 
in  an  aeroplane  while  in  flight. 

To  determine  this,  short  of  actual  experiments 
with  a  machine  in  horizontal  translation,  is  im- 
possible, unless  it  is  done  by  taking  into  account 
the  factor  due  to  momentum  and  the  element  at- 


24  AEROPLANES 

tributable  to  the  lift  of  the  plane  itself  due  to  its 
impact  against  the  atmosphere. 

LANGLEY'S  LAW. — The  law  enunciated  by 
Langley  is,  that  the  greater  the  speed  the  less  the 
power  required  to  propel  it.  "Water  as  a  pro- 
pelling medium  has  over  seven  hundred  times 
more  force  than  air.  A  vessel  having,  for  in- 
stance, twenty  horse  power,  and  a  speed  of  ten 
miles  per  hour,  would  require  four  times  that 
power  to  drive  it  through  the  water  at  double  the 
speed.  The  power  is  as  the  square  of  the  speed. 

With  air  the  conditions  are  entirely  different. 
The  boat  submergence  in  the  water  is  practically 
the  same,  whether  going  ten  or  twenty  miles  an 
hour.  The  head  resistance  is  the  same,  substan- 
tially, at  all  times  in  the  case  of  the  boat ;  with  the 
flying  machine  the  resistance  of  its  sustaining 
surfaces  decreases. 

Without  going  into  a  too  technical  description 
of  the  reasoning  which  led  to  the  discovery  of  the 
law  of  air  pressures,  let  us  try  and  understand 
it  by  examining  the  diagram,  Fig.  7. 

A  represents  a  plane  at  an  angle  of  45  degrees, 
moving  forwardly  into  the  atmosphere  in  the 
direction  of  the  arrows  B.  The  measurement 
across  the  plane  vertically,  along  the  line  B, 
which  is  called  the  sine  of  the  angle,  represents 
the  surface  impact  of  air  against  the  plane. 


THEORIES  AND  FACTS  25 

In  Fig.  8  the  plane  is  at  an  angle  of  27  degrees, 
which  makes  the  distance  in  height  across  the  line 
C  just  one-half  the  length  of  the  line  B  of  Fig.  7, 


hence  the  surface  impact  of  the  air  is  one-half  that 
of  Fig.  7,  and  the  drift  is  correspondingly  de- 
creased. 


8.  Unequal  Xift  an&Drift: 


MOVING  PLANES  vs.  WINDS.  —  In  this  way  Bois- 
set,  Duchemin,  Langley,  and  others,  determined 
the  comparative  drift,  and  those  results  have  been 


26  AEROPLANES 

largely  relied  upon  by  aviators,  and  assumed  to 
be  correct  when  applied  to  flying  machines. 

That  they  are  not  correct  has  been  proven  by 
the  Wrights  and  others,  the  only  explanation  be- 
ing that  some  errors  had  been  made  in  the  calcula- 
tions, or  that  aviators  were  liable  to  commit  er- 
rors in  observing  the  true,  angle  of  the  planes 
while  in  flight. 

MOMENTUM  NOT  CONSIDERED. — The  great  factor 
of  momentum  has  been  entirely  ignored,  and  it  is 
our  desire  to  press  the  important  point  on  those 
who  begin  to  study  the  question  of  flying  ma- 
chines. 

THE  FLIGHT  OF  BIRDS. — Volumes  have  been 
written  concerning  observations  on  the  flight  of 
birds.  The  marvel  has  been  why  do  soaring  birds 
maintain  themselves  in  space  without  flapping 
their  wings.  In  fact,  it  is  a  much  more  remark- 
able thing  to  contemplate  why  birds  which  depend 
on  flapping  wings  can  fly. 

THE  DOWNWARD  BEAT. — It  is  argued  that  the 
downward  beat  of  the  wings  is  so  much  more 
rapid  than  the  upward  motion,  that  it  gets  an  ac- 
tion on  the  air  so  as  to  force  the  body  upwardly. 
This  is  disposed  of  by  the  wing  motion  of  many 
birds,  notoriously  the  crow,  whose  lazily-flapping 
wings  can  be  readily  followed  by  the  eye,  and  the 
difference  in  movement,  if  any,  is  not  perceptible. 


THEORIES  AND  FACTS  27 

THE  CONCAVED  WING. — It  is  also  urged  that  the 
concave  on  the  under  side  of  the  wing  gives  the 
quality  of  lift.  Certain  kinds  of  beetles,  and  par- 
ticularly the  common  house  fly,  disprove  that  the- 
ory, as  their  wings  are  perfectly  flat. 

FEATHER  STKUCTUKE  CONSIDEKED. — Then  the 
feather  argument  is  advanced,  which  seeks  to 
show  that  as  each  wing  is  made  up  of  a  plurality 
of  feathers,  overlapping  each  other,  they  form  a 
sort  of  a  valved  surface,  opening  so  as  to  permit 
air  to  pass  through  them  during  the  period  of 
their  upward  movement,  and  closing  up  as  the 
wing  descends. 

It  is  difficult  to  perform  this  experiment  with 
wings,  so  as  to  show  such  an  individual  feather 
movement.  It  is  certain  that  there  is  nothing  in 
the  structure  of  the  wing  bone  and  the  feather 
connection  which  points  to  any  individual  feather 
movement,  and  our  observation  is,  that  each 
feather  is  entirely  too  rigid  to  permit  of  such  an 
opening  up  between  them. 

It  is  obvious  that  the  wing  is  built  up  in  that 
way  for  an  entirely  different  reason.  Soaring 
birds,  which  do  not  depend  on  the  flapping  mo- 
tion, have  the  same  overlapping  feather  forma- 
tion. 

WEBBED  WINGS. — Furthermore,  there  are  nu- 
merous flying  creatures  which  do  not  have  feath- 


28  AEEOPLANES 

ered  wings,  but  web-like  structures,  or  like  the 
house  fly,  in  one  continuous  and  unbroken 
plane. 

That  birds  which  fly  with  flapping  wings  derive 
their  support  from  the  air,  is  undoubtedly  true, 
and  that  the  lift  produced  is  due,  not  to  the  form, 
or  shape,  or  area  of  the  wing,  is  also  beyond  ques- 
tion. The  records  show  that  every  conceivable 
type  of  outlined  structure  is  used  by  nature ;  the 
material  and  texture  of  the  wings  themselves  dif- 
fer to  such  a  degree  that  there  is  absolutely  no 
similarity;  some  have  concaved  under  surfaces, 
and  others  have  not;  some  fly  with  rapidly  beat- 
ing wings,  and  others  with  slow  and  measured 
movements;  many  of  them  fly  with  equal  facility 
without  flapping  movements ;  and  the  proportions 
of  weight  to  wing  surface  vary  to  such  an  extent 
that  it  is  utterly  impossible  to  use  such  data  as  a 
guide  in  calculating  what  the  proper  surface 
should  be  for  a  correct  flying  machine. 

THE  ANGLE  OF  MOVEMENT. — How,  then,  it  may 
be  asked,  do  they  get  their  support?  There  must 
be  something,  in  all  this  variety  and  diversity  of 
form,  of  motion,  and  of  characteristics,  which 
supplies  the  true  answer.  The  answer  lies  in  the 
angle  of  movement  of  every  wing  motion,  which 
is  at  the  control  of  the  bird,  and  if  this  is  exam- 
ined it  will  be  found  that  it  supplies  the  correct 


THEORIES  AND  FACTS  29 

answer  to  every  type  of  wing  which  nature  has 
made. 

AN  INITIAL  IMPULSE  OK  MOVEMENT  NECESSAKY. — 
Let  A,  Fig.  9,  represent  the  section  of  a  bird's 
wing.  All  birds,  whether  of  the  soaring  or  the 
flapping  kind,  must  have  an  initial  forward  move- 
ment in  order  to  attain  flight.  This  impulse  is 
acquired  either  by  running  along  the  ground,  or 
by  a  leap,  or  in  dropping  from  a  perch.  Soaring 
birds  cannot,  by  any  possibility,  begin  flight,  un- 


less  there  is  such  a  movement  to  change  from  a 
position  of  rest  to  one  of  motion. 

In  the  diagram,  therefore,  the  bird,  in  moving 
forwardly,  while  raising  the  wing  upwardly,  de- 
presses the  rear  edge  of  the  wing,  as  in  position 
1,  and  when  the  wing  beats  downwardly  the  rear 
margin  is  raised,  in  relation  to  its  front  margin, 
as  shown  in  position  2. 

A  WEDGING  MOTION. — Thus  the  bird,  by  a 
wedge-like  motion,  gives  a  forwardly-propelling 
action,  and  as  the  rear  margin  has  more  or  less 
flexure,  its  action  against  the  air  is  less  during  its 


30 


AEROPLANES 


upward  beat,  and  this  also  adds  to  the  upward  lift 
of  the  body  of  the  bird. 

No  MYSTERY  IN  THE  WAVE  MOTION. — There  is 
no  mystery  in  the  effect  of  such  a  wave-like  mo- 
tion, and  it  must  be  obvious  that  the  humming 
bird,  and  like  flyers,  which  poise  at  one  spot,  are 


able  to  do  so  because,  instead  of  moving  for- 
wardly,  or  changing  the  position  of  its  body  hori- 
zontally, in  performing  the  undulatory  motion  of 
the  wing,  it  causes  the  body  to  rock,  so  that  at  the 
point  where  the  wing  joins  the  body,  an  elliptical 
motion  is  produced. 


THEOBIES  AND  FACTS  31 

How  BIRDS  POISE  WITH  FLAPPING  WINGS. — This 
is  shown  in  Fig.  10,  in  which  eight  successive  po- 
sitions of  the  wing  are  shown,  and  wherein  four 
of  the  position,  namely,  1,  2,  3,  and  4,  represent 
the  downward  movement,  and  6,  7,  8,  and  9,  the 
upward  beat. 

All  the  wing  angles  are  such  that  whether  the 
suspension  point  of  each  wing  is  moving  down- 
wardly, or  upwardly,  a  support  is  found  in  some 
part  of  the  wing. 

NARROW-WINGED  BIRDS. — Birds  with  rapid  flap- 
ping motions  have  comparatively  narrow  wings, 
fore  and  aft.  Those  which  flap  slowly,  and  are 
not  swift  flyers,  have  correspondingly  broader 
wings.  The  broad  wing  is  also  typical  of  the 
soaring  birds. 

But  how  do  the  latter  overcome  gravitation 
without  exercising  some  sort  of  wing  movement? 

INITIAL  MOVEMENT  OP  SOARING  BIRDS. — Acute 
observations  show  that  during  the  early  stages 
of  flight,  before  speed  is  acquired,  they  depend 
on  the  undulating  movement  of  the  wings,  and 
some  of  them  acquire  the  initial  motion  by  flap- 
ping. When  speed  is  finally  attained  it  is  diffi- 
cult for  the  eye  to  note  the  motion  of  the  wings. 

SOARING  BIRDS  MOVE  SWIFTLY. — Now,  the  first 
observation  is,  that  soaring  birds  are  swiftly- 
moving  creatures.  As  they  sail  overhead  ma- 


32  AEROPLANES 

jestically  they  seem  to  be  moving  slowly.  But 
distance  is  deceptive.  The  soaring  bird  travels 
at  great  speeds,  and  this  in  itself  should  be  suffi- 
cient to  enable  us  to  cease  wondering,  when  it  is 
remembered  that  swift  translation  decreases 
weight,  so  that  this  factor  does  not,  under  those 
conditions,  operate  against  flight. 

MUSCULAR  ENERGY  EXERTED  BY  SOARING  BIRDS. 
— It  is  not  conceivable  that  the  mere  will  of  the 
bird  would  impel  it  forwardly,  without  it  exerted 
some  muscular  energy  to  keep  up  its  speed.  The 
distance  at  which  the  bird  performs  this  wonder- 
ful evolution  is  at  such  heights  from  the  observer 
that  the  eye  cannot  detect  a  movement. 

WINGS  NOT  MOTIONLESS. — While  the  wings  ap- 
pear to  be  absolutely  motionless,  it  is  more  rea- 
sonable to  assume  that  a  slight  sinuous  movement, 
or  a  rocking  motion  is  constantly  kept  up,  which 
wedges  forwardly  with  sufficient  speed  to  compel 
momentum  to  maintain  it  in  flight.  To  do  so  re- 
quires but  a  small  amount  of  energy.  The  head 
resistance  of  the  bird  formation  is  reduced  to  a 
minimum,  and  at  such  high  speeds  the  angle  of 
incidence  of  the  wings  is  very  small,  requiring  but 
little  aid  to  maintain  it  in  horizontal  flight. 


CHAPTER  II 

PRINCIPLES   OF   AEROPLANE  FLIGHT 

FROM  the  foregoing  chapter,  while  it  may  be 
rightly  inferred  that  power  is  the  true  secret  of 
aeroplane  flight,  it  is  desirable  to  point  out  certain 
other  things  which  must  be  considered. 

SPEED  AS  ONE  OF  THE  ELEMENTS. — Every  boy, 
probably,  has  at  some  time  or  other  thrown  small 
flat  stones,  called  " skippers."  He  has  noticed 
that  if  they  are  particularly  thin,  and  large  in 
diameter,  that  there  is  a  peculiar  sailing  motion, 
and  that  they  move  through  the  air  in  an  undu- 
lating or  wave-like  path. 

Two  things  contribute  to  this  motion ;  one  is  the 
size  of  the  skipper,  relative  to  its  weight,  and  the 
other  is  its  speed.  If  the  speed  is  slow  it  will 
quickly  wend  its  way  to  the  earth  in  a  gradual 
curve.  This  curved  line  is  called  its  trajectory. 
If  it  is  not  very  large  diametrically,  in  proportion 
to  its  weight,  it  will  also  make  a  gradual  curve  in 
descending,  without  "skimming"  up  and  down 
in  its  flight. 

SHAPE  AND  SPEED. — It  has  been  observed,  also, 

33 


34  AEROPLANES 

that  a  round  ball,  or  an  object  not  flattened  out, 
will  make  a  regular  curved  path,  whatever  the 
speed  may  be. 

It  may  be  assumed,  therefore,  that  the  shape 
alone  does  not  account  for  this  sinuous  motion; 
but  that  speed  is  the  element  which  accounts  for 
it.  Such  being  the  case  it  may  be  well  to  inquire 
into  the  peculiar  action  which  causes  a  skipper 
to  dart  up  and  down,  and  why  the  path  thus 
formed  grows  more  and  more  accentuated  as  the 
speed  increases. 

As  will  be  more  fully  described  in  a  later  chap- 
ter, the  impact  of  air  against  a  moving  body  does 
not  increase  in  proportion  to  its  speed,  but  in  the 
ratio  of  the  square  of  the  speed. 

WHAT  SQUAEE  OF  THE  SPEED  MEANS. — In  math- 
ematics a  figure  is  squared  when  it  is  multiplied 
by  itself.  Thus,  4  X  4  =  16 ;  5  X  5  =  25 ;  and  so 
on,  so  that  16  is  the  square  of  4,  and  25  the  square 
of  5.  It  has  been  found  that  a  wind  moving  at  the 
speed  of  20  miles  an  hour  has  a  striking  or  pushing 
force  of  2  pounds  on  every  square  foot  of  surface. 

If  the  wind  travels  twice  as  fast,  or  40  miles 
an  hour,  the  pushing  force  is  not  4  pounds,  but 
8  pounds.  If  the  speed  is  60  miles  an  hour  the 
pushing  force  increases  to  18  pounds. 

ACTION  OF  A  SKIPPER. — When  the  skipper  leaves 
the  hands  of  the  thrower  it  goes  through  the  air 


PRINCIPLES  OF  FLIGHT 


35 


in  such  a  way  that  its  flat  surface  is  absolutely 
on  a  line  with  the  direction  in  which  it  is  pro- 
jected. 

At  first  it  moves  through  the  air  solely  by  force 
of  the  power  which  impels  it,  and  does  not  in  any 
way  depend  on  the  air  to  hold  it  up.  See  Fig. 
1,  in  which  A  represents  the  line  of  projection, 
and  B  the  disk  in  its  flight. 


After  it  has  traveled  a  certain  distance,  and 
the  force  decreases,  it  begins  to  descend,  thus  de- 
scribing the  line  C,  Fig.  1,  the  disk  B,  in  this  case 
descending,  without  changing  its  position,  which 
might  be  described  by  saying  that  it  merely  set- 
tles down  to  the  earth  without  changing  its  plane. 


36  AEROPLANES 

The  skipper  still  remains  horizontal,  so  that  as 
it  moves  toward  the  earth  its  flat  surface,  which 
is  now  exposed  to  the  action  of  the  air,  meets 
with  a  resistance,  and  this  changes  the  angle  of 
the  disk,  so  that  it  will  not  be  horizontal.  In- 
stead it  assumes  the  position  as  indicated  at  D, 
and  this  impinging  effect  against  the  air  causes 
the  skipper  to  move  upwardly  along  the  line  E, 
and  having  reached  a  certain  limit,  as  at,  say  E, 
it  automatically  again  changes  its  angle  and  moves 
downwardly  along  the  path  F,  and  thus  continues 
to  undulate,  more  or  less,  dependent  on  the  com- 
bined action  of  the  power  and  weight,  or  momen- 
tum, until  it  reaches  the  earth. 

It  is,  therefore,  clear  that  the  atmosphere  has 
an  action  on  a  plane  surface,  and  that  the  extent 
of  the  action,  to  sustain  it  in  flight,  depends  on  two 
things,  surface  and  speed. 

Furthermore,  the  greater  the  speed  the  less  the 
necessity  for  surface,  and  that  for  gliding  pur- 
poses speed  may  be  sacrificed,  in  a  large  measure, 
where  there  is  a  large  surface. 

This  very  action  of  the  skipper  is  utilized  by 
the  aviator  in  volplaning, — that  is,  where  the 
power  of  the  engine  is  cut  off,  either  by  accident, 
or  designedly,  and  the  machine  descends  to  the 
earth,  whether  in  a  long  straight  glide,  or  in  a 
great  circle. 


PRINCIPLES  OP  FLIGHT  37 

As  the  machine  nears  the  earth  it  is  caused  to 
change  the  angle  of  flight  by  the  control  mechanism 
so  that  it  will  dart  upwardly  at  an  angle,  or  down- 
wardly, and  thus  enable  the  pilot  to  sail  to  an- 
other point  beyond  where  he  may  safely  land. 
This  changing  the  course  of  the  machine  so  that 
it  will  glide  upwardly,  means  that  the  incidence 
of  the  planes  has  been  changed  to  a  positive 
angle. 

ANGLE  OF  INCIDENCE. — In  aviation  this  is  a  term 
given  to  the  position  of  a  plane,  relative  to  the 
air  against  which  it  impinges.  If,  for  instance, 
an  aeroplane  is  moving  through  the  air  with  the 
front  margin  of  the  planes  higher  than  their  rear 
margins,  it  is  said  to  have  the  planes  at  a  positive 
angle  of  incidence.  If  the  rear  margins  are 
higher  than  the  front,  then  the  planes  have  a  neg- 
ative angle  of  incidence. 

The  word  incidence  really  means,  a  falling 
upon,  or  against;  and  it  will  be  seen,  therefore, 
that  the  angle  of  incidence  means  the  tilt  of  the 
planes  in  relation  to  the  air  which  strikes  it. 

Having  in  view,  therefore,  that  the  two  quali- 
ties, namely,  speed  and  surface,  bear  an  intimate 
relation  with  each  other,  it  may  be  understood 
wherein  mechanical  flight  is  supposed  to  be  analo- 
gous to  bird  flight. 

SPEED  AND  SURFACE. — Birds  which  poise  in  the 


38  AEROPLANES 

air,  like  the  humming  bird,  do  so  because  they 
beat  their  wings  with  great  rapidity.  Those 
which  soar,  as  stated,  can  do  so  only  by  moving 
through  the  atmosphere  rapidly,  or  by  having  a 
large  wing  spread  relative  to  the  weight.  It  will 
thus  be  seen  that  speed  and  surface  become  the 
controlling  factors  in  flight,  and  that  while  the 
latter  may  be  entirely  eliminated  from  the  prob- 
lem, speed  is  absolutely  necessary  under  any  and 
all  conditions. 

By  speed  in  this  connection  is  not  meant  high 
velocity,  but  that  a  movement,  produced  by  power 
expressed  in  some  form,  is  the  sole  and  most  nec- 
essary requisite  to  movement  through  the  air  with 
all  heavier-than-air  machines. 

If  sufficient  power  can  be  applied  to  an  aero- 
plane, surface  is  of  no  consequence;  shape  need 
not  be  considered,  and  any  sort  of  contrivance 
will  move  through  the  air  horizontally. 

CONTROL  OF  THE  DIRECTION  OF  FLIGHT. — But  the 
control  of  such  a  body,  when  propelled  through 
space  by  force  alone,  is  a  different  matter.  To 
change  the  machine  from  a  straight  path  to  a 
curved  one,  means  that  it  must  be  acted  upon  by 
some  external  force. 

We  have  explained  that  power  is  something 
which  is  inherent  in  the  thing  itself.  Now,  in  or- 
der that  there  may  be  a  change  imparted  to  a 


PRINCIPLES  OF  FLIGHT  39 

moving  mass,  advantage  must  be  taken  of  the  me- 
dium through  which  it  moves, — the  atmosphere. 

VERTICAL  CONTROL  PLANES. — If  vertically-ar- 
ranged planes  are  provided,  either  fore  or  aft  of 
the  machine,  or  at  both  ends,  the  angles  of  inci- 
dence may  be  such  as  to  cause  the  machine  to 
turn  from  its  straight  course. 

In  practice,  therefore,  since  it  is  difficult  to  sup- 
ply sufficient  power  to  a  machine  to  keep  it  in  mo- 
tion horizontally,  at  all  times,  aeroplanes  are  pro- 
vided with  supporting  surfaces,  and  this  aid  in 
holding  it  up  grows  less  and  less  as  its  speed  in- 
creases. 

But,  however  strong  the  power,  or  great  the 
speed,  its  control  from  side  to  side  is  not  de- 
pendent on  the  power  of  the  engine,  or  the  speed 
at  which  it  travels  through  the  air. 

Here  the  size  of  the  vertical  planes,  and  their 
angles,  are  the  only  factors  to  be  considered,  and 
these  questions  will  be  considered  in  their  proper 
places. 


CHAPTER  III 

THE   FOBM   OB  SHAPE   OP  FLYING  MACHINES 

EVERY  investigator,  experimenter,  and  scientist, 
who  has  given  the  subject  of  flight  study,  pro- 
ceeds on  the  theory  that  in  order  to  fly  man  must 
copy  nature,  and  make  the  machine  similar  to  the 
type  so  provided. 

THE  THEORY  OP  COPYING  NATURE. — If  such  is  the 
case  then  it  is  pertinent  to  inquire  which  bird  is 
the  proper  example  to  use  for  mechanical  flight. 
We  have  shown  that  they  differ  so  radically  in 
every  essential,  that  what  would  be  correct  in  one 
thing  would  be  entirely  wrong  in  another. 

The  bi-plane  is  certainly  not  a  true  copy.  The 
only  thing  in  the  Wright  machine  which  in  any 
way  resembles  the  bird's  wing,  is  the  rounded  end 
of  the  planes,  and  judging  from  other  machines, 
which  have  square  ends,  this  slight  similarity  does 
not  contribute  to  its  stability  or  otherwise  help 
the  structure. 

The  monoplane,  which  is  much  nearer  the  bird 
type,  has  also  sounded  wing  ends,  made  not  so 

40 


THE  FORM  OF  FLYING  MACHINES     41 

much  for  the  purpose  of  imitating  the  wing  of  the 
bird,  as  for  structural  reasons. 

HULLS  OF  VESSELS. — If  some  marine  architect 
should  come  forward  and  assert  that  he  intended 
to  follow  nature  by  making  a  boat  with  a  hull  of 
the  shape  or  outline  of  a  duck,  or  other  swimming 
fowl,  he  would  be  laughed  at,  and  justly  so,  be- 
cause the  lines  of  vessels  which  are  most  efficient 
are  not  made  like  those  of  a  duck  or  other  swim- 
ming creatures. 

MAN  DOES  NOT  COPY  NATURE. — Look  about  you, 
and  see  how  many  mechanical  devices  follow  the 
forms  laid  down  by  nature,  or  in  what  respect 
man  uses  the  types  which  nature  provides  in  de- 
vising the  many  inventions  which  ingenuity  has 
brought  forth. 

PRINCIPLES  ESSENTIAL,  NOT  FORMS. — It  is  essen- 
tial that  man  shall  follow  nature's  laws.  He  can- 
not evade  the  principles  on  which  the  operations 
of  mechanism  depend;  but  in  doing  so  he  has,  in 
nearly  every  instance,  departed  from  the  form 
which  nature  has  suggested,  and  made  the  ma- 
chine irrespective  of  nature's  type. 

Let  us  consider  some  of  these  striking  differ- 
ences to  illustrate  this  fact.  Originally  pins  were 
stuck  upon  a  paper  web  by  hand,  and  placed  in 
rows,  equidistant  from  each  other.  This  necessi- 
tates the  cooperative  function  of  the  fingers  and 


42  AEKOPLANES 

the  eye.  An  expert  pin  sticker  could  thus  assem- 
ble from  four  to  five  thousand  pins  a  day. 

The  first  mechanical  pinsticker  placed  over 
500,000  pins  a  day  on  the  web,  rejecting  every  bent 
or  headless  pin,  and  did  the  work  with  greater 
accuracy  than  it  was  possible  to  do  it  by  hand. 
There  was  not  the  suggestion  of  an  eye,  or  a  finger 
in  the  entire  machine,  to  show  that  nature  fur- 
nished the  type. 

NATURE  NOT  THE  GUIDE  AS  TO  FORMS. — Nature 
does  not  furnish  a  wheel  in  any  of  its  mechan- 
ical expressions.  If  man  followed  nature's  form 
in  the  building  of  the  locomotive,  it  would  move 
along  on  four  legs  like  an  elephant.  Curiously 
enough,  one  of  the  first  road  wagons  had  "push 
legs," — an  instance  where  the  mechanic  tried  to 
copy  nature, — and  failed. 

THE  PROPELLER  TYPE. — The  well  known  propel- 
ler is  a  type  of  wheel  which  has  no  prototype  in 
nature.  It  is  maintained  that  the  tail  of  a  fish 
in  its  movement  suggested  the  propeller,  but  the 
latter  is  a  long  departure  from  it. 

The  Venetian  rower,  who  stands  at  the  stern, 
and  with  a  long-bladed  oar,  fulcrumed  to  the 
boat's  extremity,  in  making  his  graceful  lateral 
oscillations,  simulates  the  propelling  motion  of 
the  tail  in  an  absolutely  perfect  manner,  but  it  is 


THE  FOEM  OF  FLYING  MACHINES     43 

not  a  propeller,  by  any  means  comparable  to  the 
kind  mounted  on  a  shaft,  and  revoluble. 

How  much  more  efficient  are  the  spirally-formed 
blades  of  the  propeller  than  any  wing  or  fin  move- 
ment, in  air  or  sea.  There  is  no  comparison  be- 
tween the  two  forms  in  utility  or  value. 

Again,  the  connecting  points  of  the  arms  and 
legs  with  the  trunk  of  a  human  body  afford  the 
most  perfect  types  of  universal  joints  which  na- 
ture has  produced.  The  man-made  universal 
joint  has  a  wider  range  of  movement,  possesses 
greater  strength,  and  is  more  perfect  mechan- 
ically. A  universal  joint  is  a  piece  of  mechanism 
between  two  elements,  which  enables  them  to  be 
turned,  or  moved,  at  any  angle  relative  to  each 
other. 

But  why  multiply  these  instances.  Like  sam- 
ples will  be  found  on  every  hand,  and  in  all  direc- 
tions, and  man,  the  greatest  of  all  of  nature's 
products,  while  imperfect  in  himself,  is  improving 
and  adapting  the  things  he  sees  about  him. 

WHY  SPECIALLY-DESIGNED  FORMS  IMPROVE  NAT- 
URAL STRUCTURES. — The  reason  for  this  is,  pri- 
marily, that  the  inventor  must  design  the  article 
for  its  special  work,  and  in  doing  so  makes  it  bet- 
ter adapted  to  do  that  particular  thing.  The 
hands  and  fingers  can  do  a  multiplicity  of  things, 


44  'AEBOPLANES 

but  it  cannot  do  any  particular  work  with  the  fa- 
cility or  the  degree  of  perfection  that  is  possible 
with  the  machine  made  for  that  purpose. 

The  hands  and  fingers  will  bind  a  sheaf  of 
wheat,  but  it  cannot  compete  with  the  special  ma- 
chine made  for  that  purpose.  On  the  other  hand 
the  binder  has  no  capacity  to  do  anything  else  than 
what  it  was  specially  made  for. 

In  applying  the  same  sort  of  reasoning  to  the 
building  of  flying  machines  we  must  be  led  to  the 
conclusion  that  the  inventor  can,  and  will,  eventu- 
ally, bring  out  a  form  which  is  as  far  superior  to 
the  form  which  nature  has  taught  us  to  use  as 
the  wonderful  machines  we  see  all  about  us  are 
superior  to  carry  out  the  special  work  they  were 
designed  to  do. 

On  land,  man  has  shown  this  superiority  over 
matter,  and  so  on  the  sea.  Singularly,  the  sub- 
marines, which  go  beneath  the  sea,  are  very  far 
from  that  perfected  state  which  have  been  at- 
tained by  vessels  sailing  on  the  surface ;  and  while 
the  means  of  transportation  on  land  are  arriving 
at  points  where  the  developments  are  swift  and 
remarkable,  the  space  above  the  earth  has  not  yet 
been  conquered,  but  is  going  through  that  same 
period  of  development  which  precedes  the  produc- 
tion of  the  true  form  itself. 

MECHANISM  DEVOID  OF  INTELLIGENCE. — The  great 


THE  FORM  OF  FLYING  MACHINES     45 

error,  however,  in  seeking  to  copy  nature's  form 
in  a  flying  machine  is,  that  we  cannot  invest  the 
mechanism  with  that  which  the  bird  has,  namely, 
a  guiding  intelligence  to  direct  it  instinctively,  as 
the  flying  creature  does. 

A  MACHINE  MUST  HAVE  A  SUBSTITUTE  FOB  IN- 
TELLIGENCE.— Such  being  the  case  it  must  be  en- 
dowed with  something  which  is  a  substitute.  A 
bird  is  a  supple,  pliant  organism ;  a  machine  is  a 
rigid  structure.  One  is  capable  of  being  directed 
by  a  mind  which  is  a  part  of  the  thing  itself ;  while 
the  other  must  depend  on  an  intelligence  which  is 
separate  from  it,  and  not  responsive  in  feeling  or 
movement. 

For  the  foregoing  reasons  success  can  never 
be  attained  until  some  structural  form  is  devised 
which  will  consider  the  flying  machine  independ- 
ently of  the  prototypes  pointed  out  as  the  correct 
things  to  follow.  It  does  not,  necessarily,  have  to 
be  unlike  the  bird  form,  but  we  do  know  that  the 
present  structures  have  been  made  and  insisted 
upon  blindly,  because  of  this  wrong  insistence  on 
forms. 

STUDY  OF  BIKD  FLIGHT  USELESS. — The  study  of 
the  flight  of  birds  has  never  been  of  any  special 
value  to  the  art.  Volumes  have  been  written  on 
the  subject.  The  Seventh  Duke  of  Argyle,  and 
later,  Pettigrew,  an  Englishman,  contributed  a 


46  AEROPLANES 

vast  amount  of  written  matter  on  the  subject  of 
bird  flight,  in  which  it  was  sought  to  show  that 
soaring  birds  did  not  exert  any  power  in  flying. 

Writers  and  experimenters  do  not  agree  on  the 
question  of  the  propulsive  power,  or  on  the  form 
or  shape  of  the  wing  which  is  most  effective,  or 
in  the  matter  of  the  relation  of  surface  to  weight, 
nor  do  they  agree  in  any  particular  as  to  the  effect 
and  action  of  matter  in  the  soaring  principle. 

Only  a  small  percentage  of  flying  creatures  use 
motionless  wings  as  in  soaring.  By  far,  the 
greater  majority  use  beating  wings,  a  method  of 
translation  in  air  which  has  not  met  with  success 
in  any  attempts  on  the  part  of  the  inventor. 

Nevertheless,  experimenting  has  proceeded  on 
lines  which  seek  to  recognize  nature's  form  only, 
while  avoiding  the  best  known  and  most  persistent 
type. 

SHAPE  OF  SUPPORTING  SUKFACES. — When  we  ex- 
amine the  prevailing  type  of  supporting  surfaces 
we  cannot  fail  to  be  impressed  with  one  feature, 
namely,  the  determination  to  insist  on  a  broad 
spread  of  plane  surface,  in  imitation  of  the  bird 
with  outstretched  wings. 

THE  TROUBLE  ARISING  FROM  OUTSTRETCHED 
WINGS. — This  form  of  construction  is  what  brings 
all  the  troubles  in  its  train.  The  literature  on 
aviation  is  full  of  arguments  on  this  subject,  all 


THE  FORM  OF  FLYING  MACHINES     47 

declaring  that  a  wide  spread  is  essential,  because, 
— birds  fly  that  way. 

These  assertions  are  made  notwithstanding  the 
fact  that  only  a  few  years  ago,  in  the  great  exhibit 
of  aeroplanes  in  Paris,  many  unique  forms  of  ma- 
chines were  shown,  all  of  them  capable  of  flying, 
as  proven  by  numerous  experiments,  and  among 
them  were  a  half  dozen  types  whose  length  fore 
and  aft  were  much  greater  than  transversely,  and 
it  was  particularly  noted  that  they  had  most  won- 
derful stability. 

DENSITY  OF  THE  ATMOSPHEKE. — Experts  declare 
that  the  density  of  the  atmosphere  varies  through- 
out,— that  it  has  spots  here  and  there  which  are, 
apparently,  like  holes,  so  that  one  side  or  the 
other  of  the  machine  will,  unaccountably,  tilt,  and 
sometimes  the  entire  machine  will  suddenly  drop 
for  many  feet,  while  in  flight. 

ELASTICITY  OF  THE  AIR. — Air  is  the  most  elastic 
substance  known.  The  particles  constituting  it 
are  constantly  in  motion.  When  heat  or  cold  pen- 
etrate the  mass  it  does  so,  in  a  general  way,  so  as 
to  permeate  the  entire  body,  but  the  conductivity 
of  the  atmospheric  gases  is  such  that  the  heat 
does  not  reach  all  parts  at  the  same  time. 

AIR  HOLES. — The  result  is  that  varying  strata 
of  heat  and  cold  seem  to  be  superposed,  and  also 
distributed  along  the  route  taken  by  a  machine, 


48  AEROPLANES 

causing  air  currents  which  vary  in  direction  and 
intensity.  "When,  therefore,  a  rapidly-moving 
machine  passes  through  an  atmosphere  so  dis- 
turbed, the  surfaces  of  the  planes  strike  a  mass  of 
air  moving,  we  may  say,  first  toward  the  plane, 
and  the  next  instant  the  current  is  reversed,  and 
the  machine  drops,  because  its  support  is  tempo- 
rarily gone,  and  the  aviator  experiences  the  sen- 
sation of  going  into  a  "hole." 

RESPONSIBILITY  FOR  ACCIDENTS. — These  so-called 
" holes"  are  responsible  for  many  accidents.  The 
outstretched  wings,  many  of  them  over  forty  feet 
from  tip  to  tip,  offer  opportunities  for  a  tilt  at  one 
end  or  the  other,  which  has  sent  so  many  machines 
to  destruction. 

The  high  center  of  gravity  in  all  machines  makes 
the  weight  useless  to  counterbalance  the  rising 
end  or  to  hold  up  the  depressed  wing. 

All  aviators  agree  that  these  unequal  areas  of 
density  extend  over  small  spaces,  and  it  is,  there- 
fore, obvious  that  a  machine  which  is  of  such  a 
structure  that  it  moves  through  the  air  broadside 
on,  will  be  more  liable  to  meet  these  inequalities 
than  one  which  is  narrow  and  does  not  take  in  such 
a  wide  path. 

Why,  therefore,  persist  in  making  a  form  which, 
by  its  very  nature,  invites  danger?  Because  birds 
fly  that  way! 


THE  FORM  OF  FLYING  MACHINES     49 

THE  TURNING  MOVEMENT. — This  structural  ar- 
rangement accentuates  the  difficulty  when  the  ma- 
chine turns.  The  air  pressure  against  the  wing 
surface  is  dependent  on  the  speed.  The  broad  out- 
stretched surfaces  compel  the  wing  at  the  outer 
side  of  the  circle  to  travel  faster  than  the  inner 
one.  As  a  result,  the  outer  end  of  the  aeroplane 
is  elevated. 

CENTRIFUGAL  ACTION. — At  the  same  time  the 
running  gear,  and  the  frame  which  carries  it  and 
supports  the  machine  while  at  rest,  being  below 
the  planes,  a  centrifugal  force  is  exerted,  when 
turning  a  circle,  which  tends  to  swing  the  wheels 
and  frame  outwardly,  and  thereby  still  further 
elevating  the  outer  end  of  the  plane. 

THE  WAKPING  PLANES. — The  only  remedy  to 
meet  this  condition  is  expressed  in  the  mechanism 
which  wraps  or  twists  the  outer  ends  of  the  planes, 
as  constructed  in  the  Wright  machine,  or  the 
ailerons,  or  small  wings  at  the  rear  margins  of  the 
planes,  as  illustrated  by  the  Farman  machine. 
The  object  of  this  arrangement  is  to  decrease  the 
angle  of  incidence  at  the  rising  end,  and  increase 
the  angle  at  the  depressed  end,  and  thus,  by  man- 
ually-operated means  keep  the  machine  on  an  even 
keel. 


CHAPTEB  IV 

FORE   AND   AFT   CONTROL 

THERE  is  no  phase  of  the  art  of  flying  more  im- 
portant than  the  fore  and  aft  control  of  an  airship. 
Lateral  stability  is  secondary  to  this  feature,  for 
reasons  which  will  appear  as  we  develope  the 
subject. 

THE  BIRD  TYPE  OF  FORE  AND  AFT  CONTROL. — 
Every  aeroplane  follows  the  type  set  by  nature 
in  the  particular  that  the  body  is  caused  to  os- 
cillate on  a  vertical  fore  and  aft  plane  while  in 
flight.  The  bird  has  one  important  advantage, 
however,  in  structure.  Its  wing  has  a  flexure  at 
the  joint,  so  that  its  body  can  so  oscillate  inde- 
pendently of  the  angle  of  the  wings. 

The  aeroplane  has  the  wing  firmly  fixed  to  the 
body,  hence  the  only  way  in  which  it  is  possible 
to  effect  a  change  in  the  angle  of  the  wing  is  by 
changing  the  angle  of  the  body.  To  be  consistent 
the  aeroplane  should  be  so  constructed  that  the 
angle  of  the  supporting  surfaces  should  be  mov- 
able, and  not  controllable  by  the  body. 

The  bird,  in  initiating  flight  from  a  perch,  darts 

50 


FORE  AND  AFT  CONTROL  51 

downwardly,  and  changes  the  angle  of  the  body  to 
correspond  with  the  direction  of  the  flying  start. 
When  it  alights  the  body  is  thrown  so  that  its 
breast  banks  against  the  air,  but  in  ordinary  flight 
its  wings  only  are  used  to  change  the  angle  of 
flight. 

ANGLE  AND  DIRECTION  OF  FLIGHT. — In  order  to 
become  familiar  with  terms  which  will  be  fre- 
quently used  throughout  the  book,  care  should  be 
taken  to  distinguish  between  the  terms  angle  and 
direction  of  flight.  The  former  has  reference  to 
the  up  and  down  movement  of  an  aeroplane, 
whereas  the  latter  is  used  to  designate  a  turning 
movement  to  the  right  or  to  the  left. 

WHY  SHOULD  THE  ANGLE  OF  THE  BODY  CHANGE? 
— The  first  question  that  presents  itself  is,  why 
should  the  angle  of  the  aeroplane  body  change! 
Why  should  it  be  made  to  dart  up  and  down  and 
produce  a  sinuous  motion?  Why  should  its  nose 
tilt  toward  the  earth,  when  it  is  descending,  and 
raise  the  forward  part  of  the  structure  while  as- 
cending? 

The  ready  answer  on  the  part  of  the  bird-form 
advocate  is,  that  nature  has  so  designed  a  flying 
structure.  The  argument  is  not  consistent,  be- 
cause in  this  respect,  as  in  every  other,  it  is  not 
made  to  conform  to  the  structure  which  they  seek 
to  copy. 


52 


AEROPLANES 


CHANGING  ANGLE  OF  BODY  NOT  SAFE. — Further- 
more, there  is  not  a  single  argument  which  can  be 
advanced  in  behalf  of  that  method  of  building, 
which  proves  it  to  be  correct.  Contrariwise,  an 
analysis  of  the  flying  movement  will  show  that  it  is 
the  one  feature  which  has  militated  against  safety, 
and  that  machines  will  never  be  safe  so  long  as 
the  angle  of  the  body  must  be  depended  upon  to 
control  the  angle  of  flying. 


TruG  horizontal 


In  Fig.  lla  three  positions  of  a  monoplane  are 
shown,  each  in  horizontal  flight.  Let  us  say  that 
the  first  figure  A  is  going  at  40  miles  per  hour, 
the  second,  B,  at  50,  and  the  third,  C,  at  60  miles. 
The  body  in  A  is  nearly  horizontal,  the  angle  of 


FOBE  AND  AFT  CONTROL 


53 


the  plane  D  being  such  that,  with  the  tail  E  also 
horizontal,  an  even  flight  is  maintained. 

When  the  speed  increases  to  50  miles  an  hour, 
the  angle  of  incidence  in  the  plane  D  must  be  de- 
creased, so  that  the  rear  end  of  the  frame  must 
be  raised,  which  is  done  by  giving  the  tail  an  angle 
of  incidence,  otherwise,  as  the  upper  side  of  the 
tail  should  meet  the  air  it  would  drive  the  rear 
end  of  the  frame  down,  and  thus  defeat  the  at- 
tempt to  elevate  that  part. 


As  the  speed  increases  ten  miles  more,  the  tail 
is  swung  down  still  further  and  the  rear  end  of 
the  frame  is  now  actually  above  the  plane  of  flight. 
In  order,  now,  to  change  the  angle  of  flight,  with- 
out altering  the  speed  of  the  machine,  the  tail  is 
used  to  effect  the  control. 

Examine  the  first  diagram  in  Fig.  12.    This 


54  AEROPLANES 

shows  the  tail  E  still  further  depressed,  and  the 
air  striking  its  lower  side,  causes  an  upward  move- 
ment of  the  frame  at  that  end,  which  so  much  de- 
creases the  angle  of  incidence  that  the  aeroplane 
darts  downwardly. 

In  order  to  ascend,  the  tail,  as  shown  in  the  sec- 
ond diagram,  is  elevated  so  as  to  depress  the  rear 
end,  and  now  the  sustaining  surface  shoots  up- 
wardly. 

Suppose  that  in  either  of  the  positions  1  or  2, 
thus  described,  the  aviator  should  lose  control  of 
the  mechanism,  or  it  should  become  deranged  or 
" stick,"  conditions  which  have  existed  in  the  his- 
tory of  the  art,  what  is  there  to  prevent  an  acci- 
dent? 

In  the  first  case,  if  there  is  room,  the  machine 
will  loop  the  loop,  and  in  the  second  case  the  ma- 
chine will  move  upwardly  until  it  is  vertical,  and 
then,  in  all  probability,  as  its  propelling  power  is 
not  sufficient  to  hold  it  in  that  position,  like  a 
helicopter,  and  having  absolutely  no  wing  sup- 
porting surface  when  in  that  position,  it  will  dart 
down  tail  foremost. 

A  NON-CHANGING  BODY. — We  may  contrast  the 
foregoing  instances  of  flight  with  a  machine  hav- 
ing the  sustaining  planes  hinged  to  the  body  in 
such  a  manner  as  to  make  the  disposition  of  its 


FOEE  AND  AFT  CONTROL 


55 


angles  synchronous  with  the  tail.  In  other  words, 
see  how  a  machine  acts  that  has  the  angle  of  flight 
controllable  by  both  planes, — that  is,  the  sustain- 
ing planes,  as  well  as  the  tail. 


COM  Helper  four. 


QQ  Mile6  perkou* 


.  Flawed   on.  A/on 


In  Fig.  13  let  the  body  of  the  aeroplane  be  hori- 
zontal, and  the  sustaining  planes  B  disposed  at 
the  same  angle,  which  we  will  assume  to  be  15 
degrees,  this  being  the  imaginary  angle  for  illus- 
trative purposes,  with  the  power  of  the  machine 
to  drive  it  along  horizontally,  as  shown  in  posi- 
tion 1. 

In  position  2  the  angles  of  both  planes  are  now 
at  10  degrees,  and  the  speed  60  miles  an  hour, 
which  still  drives  the  machine  forward  hori- 
zontally. 

In  position  3  the  angle  is  still  less,  being  now 


56 


AEROPLANES 


only  5  degrees  but  the  speed  is  increased  to  80 
miles  per  hour,  but  in  each  instance  the  body  of 
the  machine  is  horizontal. 

Now  it  is  obvious  that  in  order  to  ascend,  in 
either  case,  the  changing  of  the  planes  to  a  greater 
angle  would  raise  the  machine,  but  at  the  same 
time  keep  the  body  on  an  even  keel. 


SOAdile  s 


hour 


DESCENDING  POSITIONS  BY  POWER  CONTROL. — In 
Fig.  14  the  planes  are  the  same  angles  in  the  three 
positions  respectively,  as  in  Fig.  13,  but  now  the 
power  has  been  reduced,  and  the  speeds  are  30, 
25,  and  20  miles  per  hour,  in  positions  A,  B  and  C. 

Suppose  that  in  either  position  the  power  should 
cease,  and  the  control  broken,  so  that  it  would  be 


FORE  AND  AFT  CONTROL 


57 


impossible  to  move  the  planes.  When  the  machine 
begins  to  lose  its  momentum  it  will  descend  on  a 
curve  shown,  for  instance,  in  Fig.  15,  where  posi- 
tion 1  of  Fig.  14  is  taken  as  the  speed  and  angles 
of  the  plane  when  the  power  ceased. 


fttomentum, 


CUTTING  OFF  THE  POWER.  —  This  curve,  A,  may 
reach  that  point  where  momentum  has  ceased  as 
a  forwardly-propelling  factor,  and  the  machine 
now  begins  to  travel  rearwardly.  (Fig.  16.)  It 
has  still  the  entire  supporting  surfaces  of  the 
planes.  It  cannot  loop-the-loop,  as  in  the  instance 
where  the  planes  are  fixed  immovably  to  the  body. 

Carefully  study  the  foregoing  arrangement,  and 
it  will  be  seen  that  it  is  more  nearly  in  accord  with 
the  true  flying  principle  as  given  by  nature  than 
the  vaunted  theories  and  practices  now  indulged 
in  and  so  persistently  adhered  to. 


58  AEROPLANES 

The  body  of  a  flying  machine  should  not  be  oscil- 
lated like  a  lever.  The  support  of  the  aeroplane 
should  never  be  taken  from  it.  While  it  may  be 
impossible  to  prevent  a  machine  from  coming 
down,  it  can  be  prevented  from  overturning,  and 
this  can  be  done  without  in  the  least  detracting 
from  it  structurally. 


flane  action  — 

Ffyte. 

The  plan  suggested  has  one  great  fault,  how- 
ever. It  will  be  impossible  with  such  a  structure 
to  cause  it  to  fly  upside  down.  It  does  not  present 
any  means  whereby  dare-devil  stunts  can  be  per- 
formed to  edify  the  grandstand.  In  this  respect 
it  is  not  in  the  same  class  with  the  present  types. 

THE  STARTING  MOVEMENT. — Examine  this  plan 
from  the  position  of  starting,  and  see  the  ad- 
vantages it  possesses.  In  these  illustrations  we 
have  used,  for  convenience  only,  the  monoplane 


FORE  AND  AFT  CONTROL  59 

type,  and  it  is  obvious  that  the  same  remarks  ap- 
ply to  the  bi-plane. 

Fig.  17  shows  the  starting  position  of  the  stock 
monoplane,  in  position  1,  while  it  is  being  initially 
run  over  the  ground,  preparatory  to  launching. 
Position  2  represents  the  negative  angle  at  which 


.  circle  ofJ3odLy: 

the  tail  is  thrown,  which  movement  depresses  the 
rear  end  of  the  frame  and  thus  gives  the  support- 
ing planes  the  proper  angle  to  raise  the  machine, 
through  a  positive  angle  of  incidence,  of  the  plane. 
THE  SUGGESTED  TYPE. — In  Fig.  18  the  suggested 
type  is  shown  with  the  body  normally  in  a  hori- 
zontal position,  and  the  planes  in  a  neutral  posi- 
tion, as  represented  in  position  1.  When  suffi- 
cient speed  had  been  attained  both  planes  are 
turned  to  the  same  angle,  as  in  position  2,  and 


60  AEROPLANES 

flight  is  initiated  without  the  abnormal  oscillating 
motion  of  the  body. 

But  now  let  us  see  what  takes  place  the  moment 
the  present  type  is  launched.  If,  by  any  error  on 
the  part  of  the  aviator,  he  should  fail  to  readjust 
the  tail  to  a  neutral  or  to  a  proper  angle  of  inci- 
dence, after  leaving  the  ground,  the  machine  would 
try  to  perform  an  over-head  loop. 


V 


The  suggested  plan  does  not  require  this  cau- 
tion. The  machine  may  rise  too  rapidly,  or  its 
planes  may  be  at  too  great  an  angle  for  the  power 
or  the  speed,  or  the  planes  may  be  at  too  small  an 
angle,  but  in  either  case,  neglect  would  not  tur» 
the  machine  to  a  dangerous  position. 

These  suggestions  are  offered  to  the  novice,  be- 
cause they  go  to  the  very  foundation  of  a  correct 
understanding  of  the  principles  involved  in  the 
building  and  in  the  manipulation  of  flying  ma- 


FOBE  AND  AFT  CONTROL  61 

chines,  and  while  they  are  counter  to  the  beliefs  of 
aviators,  as  is  shown  by  the  persistency  in  adher- 
ing to  the  old  methods,  are  believed  to  be  mechan- 
ically correct,  and  worthy  of  consideration. 

THE  Low  CENTER  OF  GRAVITY. — But  we  have  still 
to  examine  another  feature  which  shows  the  wrong 
principle  in  the  fixed  planes.  The  question  is 
often  asked,  why  do  the  builders  of  aeroplanes 
place  most  of  the  weight  up  close  to  the  planes'? 
It  must  be  obvious  to  the  novice  that  the  lower 
the  weight  the  less  liability  of  overturning. 


formal  £li$M,  cvtffi  7>?'ope2ter  pulling. 


•  FORE  AND  AFT  OSCILIATIONS.  —  The  answer  is, 
that  when  the  weight  is  placed  below  the  planes  it 
acts  like  a  pendulum.  When  the  machine  is  trav- 
eling forward,  and  the  propeller  ceases  its  motion, 
as  it  usually  does  instantaneously,  the  weight,  be- 
ing below,  and  having  a  certain  momentum,  con- 
tinues to  move  on,  and  the  plane  surface  meeting 
the  resistance  just  the  same,  and  having  no  means 
to  push  it  forward,  a  greater  angle  of  resistance  is 
formed. 

In  Fig.  19  this  action  of  the  two  forces  is  illus- 


62  AEROPLANES 

trated.  The  plane  at  the  speed  of  30  miles  is  at 
an  angle  of  15  degrees,  the  body  B  of  the  machine 
being  horizontal,  and  the  weight  C  suspended  di- 
rectly below  the  supporting  surfaces. 

The  moment  the  power  ceases  the  weight  con- 
tiues  moving  f orwardly,  and  it  swings  the  forward 
end  of  the  frame  upwardly,  Fig.  20,  and  we  now 


.A 
3? 
J^fy.j&O.  c/lct,ton  when  ttopellej  ceatei  lopull. 

have,  as  in  the  second  figure,  a  new  angle  of  inci- 
dence, which  is  30  degrees,  instead  of  12.  It  will 
be  understood  that  in  order  to  effect  a  change  in 
the  position  of  the  machine,  the  forward  end  as- 
cends, as  shown  by  the  dotted  line  A. 

The  weight  C  having  now  ascended  as  far  as 
possible  forward  in  its  swing,  and  its  motion 
checked  by  the  banking  action  of  the  plan  it  will 
again  swing  back,  and  again  carry  with  it  the 
frame,  thus  setting  up  an  oscillation,  which  is  ex- 
tremely dangerous. 

The  tail  E,  with  its  unchanged  angle,  does  not, 
in  any  degree,  aid  in  maintaining  the  frame  on 
an  even  keel.  Being  nearly  horizontal  while  in 


FOEE  AND  AFT  CONTROL  63 

flight,  if  not  at  a  negative  angle,  it  actually  assists 
the  forward  end  of  the  frame  to  ascend. 

APPLICATION  OF  THE  NEW  PRINCIPLE. — Extending 
the  application  of  the  suggested  form,  let  us  see 
wherein  it  will  prevent  this  pendulous  motion  at 
the  moment  the  power  ceases  to  exert  a  forwardly- 
propelling  force. 

In  Fig.  21  the  body  A  is  shown  to  be  equipped 
with  the  supporting  plane  B  and  the  tail  C,  so 


they  are  adjustable  simultaneously  at  the  same 
angle,  and  the  weight  D  is  placed  below,  similar  to 
the  other  structure. 

At  every  moment  during  the  forward  move- 
ment of  this  type  of  structure,  the  rear  end  of 
the  machine  has  a  tendency  to  move  upwardly, 
the  same  as  the  forward  end,  hence,  when  the 
weight  seeks,  in  this  case  to  go  on,  it  acts  on  the 
rear  plane,  or  tail,  and  causes  that  end  to  raise, 
and  thus  by  mutual  action,  prevents  any  pen- 
dulous swing. 

Low  WEIGHT  NOT  NECESSARY  WITH  SYNCHRON- 


64  AEROPLANES 

OUSLY-MOVING  WINGS. — A  little  reflection  will  con- 
vince any  one  that  if  the  two  wings  move  in  har- 
mony, the  weight  does  not  have  to  be  placed  low, 
and  thus  still  further  aid  in  making  a  compact 
machine.  By  increasing  the  area  of  the  tail,  and 
making  that  a  true  supporting  surface,  instead  of 
a  mere  idler,  the  weight  can  be  moved  further 
back,  the  distance  transversely  across  the  planes 
may  be  shortened,  and  in  that  way  still  further 
increase  the  lateral  stability. 


CHAPTER  V 

DIFFERENT    MACHINE    TYPES    AND   THEIR    CHARACTER- 
ISTICS 

THERE  are  three  distinct  types  of  heavier-than- 
air  machines,  which  are  widely  separated  in  all 
their  characteristics,  so  that  there  is  scarcely  a 
single  feature  in  common. 

Two  of  them,  the  aeroplane,  and  the  orthopter, 
have  prototypes  in  nature,  and  are  distinguished 
by  their  respective  similarities  to  the  soaring 
birds,  and  those  with  flapping  wings. 

The  Helicopter,  on  the  other  hand,  has  no  an- 
tecedent type,  but  is  dependent  for  its  raising 
powers  on  the  pull  of  a  propeller,  or  a  plurality 
of  them,  constructed,  as  will  be  pointed  out  here- 
inafter. 

AEROPLANES. — The  only  form  which  has  met 
with  any  success  is  the  aeroplane,  which,  in 
practice,  is  made  in  two  distinct  forms,  one  with 
a  single  set  of  supporting  planes,  in  imitation  of 
birds,  and  called  a  monoplane;  and  the  other  hav- 
ing two  wings,  one  above  the  other,  and  called 
the  bi-plane,  or  two-planes. 

65 


66  AEROPLANES 

All  machines  now  on  the  market  which  do  not 
depend  on  wing  oscillations  come  under  those 
types. 

THE  MONOPLANE. — The  single  plane  type  has 
some  strong  claims  for  support.  First  of  these 
is  the  comparatively  small  head  resistance,  due 
to  the  entire  absence  of  vertical  supporting  posts, 
which  latter  are  necessary  with  the  biplane  type. 
The  bracing  supports  which  hold  the  outer  ends 
of  the  planes  are  composed  of  wires,  which  offer 
but  little  resistance,  comparatively,  in  flight. 

ITS  ADVANTAGES. — Then  the  vertical  height  of 
the  machine  is  much  less  than  in  the  biplane.  As 
a  result  the  weight,  which  is  farther  below  the 
supporting  surface  than  in  the  biplane,  aids  in 
maintaining  the  lateral  stability,  particularly 
since  the  supporting  frame  is  higher. 

Usually,  for  the  same  wing  spread,  the  mono- 
plane is  narrower,  laterally,  which  is  a  further 
aid  to  prevent  tilting. 

ITS  DISADVANTAGES. — But  it  also  has  disadvan- 
tages which  must  be  apparent  from  its  struc- 
ture. As  all  the  supporting  surface  is  concen- 
trated in  half  the  number  of  planes,  they  must 
be  made  of  greater  width  fore  and  aft,  and  this, 
as  we  shall  see,  later  on,  proves  to  be  a  disadvan- 
tage. 

It  is  also  doubted  whether  the  monoplane  can 


DIFFERENT  MACHINE  TYPES        67 

be  made  as  strong  structurally  as  the  other  form, 
owing  to  the  lack  of  the  truss  formation  which  is 
the  strong  point  with  the  superposed  frame.  A 
truss  is  a  form  of  construction  where  braces  can 
be  used  from  one  member  to  the  next,  so  as  to 
brace  and  stiffen  the  whole. 

THE  BIPLANE. — Nature  does  not  furnish  a  type 
of  creature  which  has  superposed  wings.  In  this 
particular  the  inventor  surely  did  not  follow  na- 
ture. The  reasons  which  led  man  to  employ  this 
type  may  be  summarized  as  follows : 

In  experimenting  with  planes  it  is  found  that 
a  broad  fore  and  aft  surface  will  not  lift  as  much 
as  a  narrow  plane.  This  subject  is  fully  ex- 
plained in  the  chapter  on  The  Lifting  Surfaces  of 
Planes.  In  view  of  that  the  technical  descrip- 
tions of  the  operation  will  not  be  touched  upon 
at  this  place,  except  so  far  as  it  may  be  necessary 
to  set  forth  the  present  subject. 
.  This  peculiarity  is  due  to  the  accumulation  of 
a  mass  of  moving  air  at  the  rear  end  of  the  plane, 
which  detracts  from  its  lifting  power.  As  it 
would  be  a  point  of  structural  weakness  to  make 
the  wings  narrow  and  very  long,  Wenham  many 
years  ago  suggested  the  idea  of  placing  one  plane 
above  the  other,  and  later  on  Chanute,  an 
engineer,  used  that  form  almost  exclusively,  in 
experimenting  with  his  gliders. 


68  AEROPLANES 

It  was  due  to  his  influence  that  the  Wrights 
adopted  that  form  in  their  gliding  experiments, 
and  later  on  constructed  their  successful  flyers 
in  that  manner.  Originally  the  monoplane  was 
the  type  generally  employed  by  experimenters, 
such  as  Lilienthal,  and  others. 

STABILITY  IN  BIPLANES. — Biplanes  are  not  nat- 
urally as  stable  laterally  as  the  monoplane. 
The  reason  is,  that  a  downward  tilt  has  the  bene- 
fit of  only  a  narrow  surface,  comparable  with  the 
monoplane,  which  has  broadness  of  wing. 

To  illustrate  this,  let  us  assume  that  we  have 
a  biplane  with  planes  five  feet  from  front  to  rear, 
and  thirty-six  feet  in  length.  This  would  give 
two  planes  with  a  sustaining  surface  of  360  square 
feet.  The  monoplane  would,  probably,  divide 
this  area  into  one  plane  eight  and  a  half  feet  from 
front  to  rear,  and  42  feet  in  length. 

In  the  monoplane  each  wing  would  project  out 
about  three  feet  more  on  each  side,  but  it  would 
have  eight  and  a  half  feet  fore  and  aft  spread 
to  the  biplane's  five  feet,  and  thus  act  as  a  greater 
support. 

THE  ORTHOPTEE. — The  term  orthopter,  or  orni- 
thopter,  meaning  bird  wing,  is  applied  to  such 
flying  machines  as  depend  on  wing  motion  to  sup- 
port them  in  the  air. 

Unquestionably,  a  support  can  be  obtained  by 


DIFFERENT  MACHINE  TYPES        69 

beating  on  the  air  but  to  do  so  it  is  necessary  to 
adopt  the  principle  employed  by  nature  to  secure 
an  upward  propulsion.  As  pointed  out  else- 
where, it  cannot  be  the  concaved  type  of  wing, 
or  its  shape,  or  relative  size  to  the  weight  it  must 
carry. 

As  nature  has  furnished  such  a  variety  of  data 
on  these  points,  all  varying  to  such  a  remarkable 
degree,  we  must  look  elsewhere  to  find  the  secret. 
Only  one  other  direction  offers  any  opportunity, 
and  that  is  in  the  individual  wing  movement. 

NATUKE'S  TYPE  NOT  UNIFORM. — When  this  is 
examined,  the  same  obscurity  surrounds  the  issue. 
Even  the  speeds  vary  to  such  an  extent  that  when 
it  is  tried  to  differentiate  them,  in  comparison 
with  form,  shape,  and  construction,  the  experi- 
menter finds  himself  wrapt  in  doubt  and  perplex- 
ity. 

But  birds  do  fly,  notwithstanding  this  wonder- 
ful array  of  contradictory  exhibitions.  Observa- 
tion has  not  enabled  us  to  learn  why  these  things 
are  so.  High  authorities,  and  men  who  are  ex- 
pert aviators,  tell  us  that  the  bird  flies  because 
it  is  able  to  pick  out  ascending  air  currents. 

THEORIES  ABOUT  FLIGHT  OF  BIRDS. — Then  we 
are  offered  the  theory  that  the  bird  has  an  in- 
stinct which  tells  it  just  how  to  balance  in  the 
air  when  its  wings  are  once  set  in  motion.  Fre- 


70  AEROPLANES 

quently,  what  is  taken  for  instinct,  is  something 
entirely  different. 

It  has  been  assumed,  for  instance,  that  a  cyclist 
making  a  turn  at  a  rapid  speed,  and  a  bird  flying 
around  a  circle  will  throw  the  upper  part  of  the 
body  inwardly  to  counteract  the  centrifugal  force 
which  tends  to  throw  it  outwardly. 

Experiments  with  the  monorail  car,  which  is 
equipped  with  a  gyroscope  to  hold  it  in  a  vertical 
position,  show  that  when  the  car  approaches  a 
curve  the  car  will  lean  inwardly,  exactly  the  same 
as  a  bird,  or  a  cyclist,  and  when  a  straight  stretch 
is  reached,  it  will  again  straighten  up. 

INSTINCT. — Now,  either  the  car,  so  equipped 
possesses  instinct,  or  there  must  be  a  principle 
in  the  laws  of  nature  which  produces  the  similar- 
ity of  action. 

In  like  manner  there  must  be  some  principle 
that  is  entirely  independent  of  the  form  of  mat- 
ter, or  its  arrangement,  which  enables  the  bird 
to  perform  its  evolutions.  We  are  led  to  believe 
from  all  the  foregoing  considerations  that  it  is 
the  manner  or  the  form  of  the  motion. 

MODE  OF  MOTION. — In  this  respect  it  seems  to 
be  comparable  in  every  respect  to  the  great  and 
universal  law  of  the  motions  in  the  universe. 
Thus,  light,  heat  and  electricity  are  the  same,  the 


DIFFERENT  MACHINE  TYPES        71 

manifestations  being  unlike  only  because  they 
have  different  modes  of  motion. 

Everything  in  nature  manifests  itself  by  mo- 
tion. It  is  the  only  way  in  which  nature  acts. 
Every  transformation  from  one  thing  to  another, 
is  by  way  of  a  movement  which  is  characteristic 
in  itself. 

Why,  then,  should  this  great  mystery  of  na- 
ture, act  unlike  the  other  portions  of  which  it  is 
a  part? 

THE  WING  STRUCTURE. — The  wing  structure  of 
every  flying  creature  that  man  has  examined,  has 
one  universal  point  of  similarity,  and  that  is  the 
manner  of  its  connection  with  the  body.  It  is  a 
sort  of  universal  joint,  which  permits  the  wing 
to  swing  up  and  down,  perform  a  gyratory  move- 
ment while  doing  so,  and  folds  to  the  rear  when 
at  rest. 

Some  have  these  movements  in  a  greater  or 
less  degree,  or  capable  of  a  greater  range;  but 
the  joint  is  the  same,  with  scarcely  an  exception. 
When  the  stroke  of  the  wing  is  downwardly  the 
rear  margin  is  higher  than  the  front  edge,  so 
that  the  downward  beat  not  only  raises  the  body 
upwardly,  but  also  propels  it  forwardly. 

THE  WING  MOVEMENT. — The  moment  the  wing 
starts  to  swing  upwardly  the  rear  end  is  de- 


72  AEROPLANES 

pressed,  and  now,  as  the  bird  is  moving  for- 
wardly,  the  wing  surface  has  a  positive  angle  of 
incidence,  and  as  the  wing  rises  while  the  for- 
ward motion  is  taking  place,  there  is  no  resist- 
ance which  is  effective  enough  to  counteract  the 
momentum  which  has  been  set  up. 

The  great  problem  is  to  put  this  motion  into  a 
mechanical  form.  The  trouble  is  not  ascribable 
to  the  inability  of  the  mechanic  to  describe  this 
movement.  It  is  an  exceedingly  simple  one. 
The  first  difficulty  is  in  the  material  that  must 
be  used.  Lightness  and  strength  for  the  wing 
itself  are  the  first  requirements.  Then  rigidity 
in  the  joint  and  in  the  main  rib  of  the  wing,  are 
the  next  considerations. 

In  these  respects  the  ability  of  man  is  limited. 
The  wing  ligatures  of  flying  creatures  is  exceed- 
ingly strong,  and  flexible ;  the  hollow  bone  forma- 
tion and  the  feathers  are  extremely  light,  com- 
pared with  their  sustaining  powers. 

THE  HELICOPTER  MOTION. — The  helicopter,  or 
helix-iving,  is  a  form  of  flying  machine  which  de- 
pends on  revolving  screws  to  maintain  it  in  the 
air.  Many  propellers  are  now  made,  six  feet  in 
length,  which  have  a  pull  of  from  400  to  500 
pounds.  If  these  are  placed  on  vertically-dis- 
posed shafts  they  would  exert  a  like  power  to 
raise  a  machine  from  the  earth. 


DIFFERENT  MACHINE  TYPES        73 

Obviously,  it  is  difficult  to  equip  such  a  machine 
with  planes  for  sustaining  it  in  flight,  after  it  is 
once  in  the  air,  and  unless  such  means  are  pro- 
vided the  propellers  themselves  must  be  the 
mechanism  to  propel  it  horizontally. 

This  means  a  change  of  direction  of  the  shafts 
which  support  the  propellers,  and  the  construc- 
tion is  necessarily  more  complicated  than  if  they 
were  held  within  non-changeable  bearings. 

This  principle,  however,  affords  a  safer  means 
of  navigating  than  the  orthopter  type,  because 
the  blades  of  such  an  instrument  can  be  forced 
through  the  air  with  infinitely  greater  speed  than 
beating  wings,  and  it  devolves  on  the  inventor  to 
devise  some  form  of  apparatus  which  will  permit 
the  change  of  pull  from  a  vertical  to  a  horizontal 
direction  while  in  flight. 


CHAPTER  VI 

THE   LIFTING   SUKFACES   OF   AEROPLANES 

THIS  subject  includes  the  form,  shape  and  angle 
of  planes,  used  in  flight.  It  is  the  direction  in 
which  most  of  the  energy  has  been  expended  in 
developing  machines,  and  the  true  form  is  still 
involved  in  doubt  and  uncertainty. 

RELATIVE  SPEED  AND  ANGLE. — The  relative 
speed  and  angle,  and  the  camber,  or  the  curved 
formation  of  the  plane,  have  been  considered  in 
all  their  aspects,  so  that  the  art  in  this  respect  has 
advanced  with  rapid  strides. 

NARROW  PLANES  MOST  EFFECTIVE. — It  was 
learned,  in  the  early  stages  of  the  development 
by  practical  experiments,  that  a  narrow  plane, 
fore  and  aft,  produces  a  greater  lift  than  a  wide 
one,  so  that,  assuming  the  plane  has  100  square 
feet  of  sustaining  surface,  it  is  far  better  to  make 
the  shape  five  feet  by  twenty  than  ten  by  ten. 

However,  it  must  be  observed,  that  to  use  the 
narrow  blade  effectively,  it  must  be  projected 
through  the  air  with  the  long  margin  forwardly. 
74 


THE  LIFTING  SURFACES  75 

Its  sustaining  power  per  square  foot  of  surface 
is  much  less  if  forced  through  the  air  lengthwise. 
Experiments  have  shown  why  a  narrow  blade 
has  proportionally  a  greater  lift,  and  this  may 
be  more  clearly  understood  by  examining  the  illus- 
trations which  show  the  movement  of  planes 
through  the  air  at  appropriate  angles. 


along  a-planc/. 

STREAM  LINES  ALONG  A  PLANE.  —  In  Fig.  22,  A 
is  a  flat  plane,  which  we  will  assume  is  10  feet 
from  the  front  to  the  rear  margin.  For  con- 
venience seven  stream  lines  of  air  are  shown, 
which  contact  with  this  inclined  surface.  The  first 
line  1,  after  the  contact  at  the  forward  end,,  is 
driven  downwardly  along  the  surface,  so  that  it 
forms  what  we  might  term  a  moving  film. 

The  second  air  stream  2,  strikes  the  first  stream, 
followed  successively  by  the  other  streams,  3,  4, 
and  so  on,  each  succeeding  stream  being  compelled 
to  ride  over,  or  along  on  the  preceding  mass  of 


76  AEROPLANES 

cushioned  air,  the  last  lines,  near  the  lower  end, 
being,  therefore,  at  such  angles,  and  contacting 
with  such  a  rapidly-moving  column,  that  it  pro- 
duces but  little  lift  in  comparison  with  the  1st, 
2d  and  3d  stream  lines.  These  stream  lines  are 
taken  by  imagining  that  the  air  approaches  and 
contacts  with  the  plane  only  along  the  lines  in- 
dicated in  the  sketch,  although  they  also  in  prac- 
tice are  active  against  every  part  of  the  plane. 

THE  CENTER  OF  PRESSURE. — In  such  a  plane  the 
center  of  pressure  is  near  its  upper  end,  probably 
near  the  line  3,  so  that  the  greater  portion  of  the 
lift  is  exerted  by  that  part  of  the  plane  above 
line  3. 

AIR  LINES  ON  THE  UPPER  SIDE  OF  THE  PLANE. — 
Now,  another  factor  must  be  considered,  namely, 
the  effect  produced  on  the  upper  side  of  the  plane, 
over  which  a  rarefied  area  is  formed  at  certain 
points,  and,  in  practice,  this  also  produces,  or 
should  be  utilized  to  effect  a  lift. 

RAREFIED  AREA. — What  is  called  a  rarefied  area, 
has  reference  to  a  state  or  condition  of  the  atmos- 
phere which  has  less  than  the  normal  pressure  or 
quantity  of  air.  Thus,  the  pressure  at  sea  level, 
is  about  14%  per  square  inch. 

As  we  ascend  the  pressure  grows  less,  and  the 
air  is  thus  rarer,  or,  there  is  less  of  it.  This  is  a 
condition  which  is  normally  found  in  the  atmos- 


THE  LIFTING  SURFACES  77 

phere.  Several  things  tend  to  make  a  rarefied 
condition.  One  is  altitude,  to  which  we  have  just 
referred. 

Then  heat  will  expand  air,  making  it  less  dense, 
or  lighter,  so  that  it  will  move  upwardly,  to  be 
replaced  by  a  colder  body  of  air.  In  aeronautics 
neither  of  these  conditions  is  of  any  importance 
in  considering  the  lifting  power  of  aeroplane  sur- 
faces. 

RAREFACTION  PRODUCED  BY  MOTION. — The  third 
rarefied  condition  is  produced  by  motion,  and  gen- 
erally the  area  is  very  limited  when  brought  about 
by  this  means.  If,  for  instance,  a  plane  is  held 
horizontally  and  allowed  to  fall  toward  the  earth, 
it  will  be  retarded  by  two  forces,  namely,  compres- 
sion and  rarefaction,  the  former  acting  on  the 
under  side  of  the  plane,  and  the  latter  on  the  upper 
side. 

Of  the  two  rarefaction  is  the  most  effectual, 
and  produces  a  greater  effect  than  compression. 
This  may  be  proven  by  compressing  air  in  a  long 
pipe,  and  noting  the  difference  in  gauge  pressure 
between  the  ends,  and  then  using  a  suction  pump 
on  the  same  pipe. 

When  a  plane  is  forced  through  the  air  at  any 
angle,  a  rarefied  area  is  formed  on  the  side  which 
is  opposite  the  one  having  the  positive  angle  of 
incidence. 


78  AEROPLANES 

If  the  plane  can  be  so  formed  as  to  make  a  large 
and  effective  area  it  will  add  greatly  to  the  value 
of  the  sustaining  surface. 

Unfortunately,  the  long  flat  plane  does  not  lend 
any  aid  in  this  particular,  as  the  stream  line  flows 
down  along  the  top,  as  shown  in  Fig.  23,  without 
being  of  any  service. 


THE  CONCAVED  PLANE. — These  considerations 
led  to  the  adoption  of  the  concaved  plane  forma- 
tion, and  for  purposes  of  comparison  the  diagram, 
Fig.  24,  shows  the  plane  B  of  the  same  length  and 
angle  as  the  straight  planes. 

In  examining  the  successive  stream  lines  it  will 
be  found  that  while  the  1st,  2d  and  3d  lines  have 
a  little  less  angle  of  impact  than  the  correspond- 
ing lines  in  the  straight  plane,  the  last  lines,  5,  6 
and  7,  have  much  greater  angles,  so  that  only  line 
4  strikes  the  plane  at  the  same  angle. 

Such  a  plane  structure  would,  therefore,  have 
its  center  of  pressure  somewhere  between  the 


THE  LIFTING  SURFACES  79 

lines  3  and  4,  and  the  lift  being  thus,  practically, 
uniform  over  the  surface,  would  be  more  effective. 
THE  CENTEB  OF  PEESSUKE. — This  is  a  term  used 
to  indicate  the  place  on  the  plane  where  the  air 
acts  with  the  greatest  force.  It  has  reference  to 
a  point  between  the  front  and  rear  margins  on-ly 
of  the  plane. 


J*  'ig.&l.JZir2ine4  fieloar  Q,  conccut&d  Plane: 

UTILIZING  THE  RAREFIED  AREA. — This  structure, 
however,  has  another  important  advantage,  as  it 
utilizes  the  rarefied  area  which  is  produced,  and 
which  may  be  understood  by  reference  to  Fig.  25. 

The  plane  B,  with  its  upward  curve,  and  at  the 
same  angle  as  the  straight  plane,  has  its  lower 
end  so  curved,  with  relation  to  the  forward  move- 
ment, that  the  air,  in  rushing  past  the  upper  end, 
cannot  follow  the  curve  rapidly  enough  to  main- 
tain the  same  density  along  C,  hence  this  exerts 


80  AEROPLANES 

an  upward  pull,  due  to  the  rarefied  area,  which 
serves  as  a  lifting  force,  as  well  as  the  compressed 
mass  beneath  the  plane. 

CHANGING  CENTER  OF  PRESSURE. — The  center  of 
pressure  is  not  constant.  It  changes  with  the 
angle  of  the  plane,  but  the  range  is  considerably 
less  on  a  concave  surface  than  on  a  flat  plane. 


^  "Up.  £5.  t/lir  fined  above  &  co/tt^ex  ItcLttQ. 

In  a  plane  disposed  at  a  small  angle,  A,  as  in 
Fig.  26,  the  center  of  pressure  is  nearer  the  for- 
ward end  of  the  plane  than  with  a  greater  posi- 
tive angle  of  incidence,  as  in  Fig.  27,  and  when 
the  plane  is  in  a  normal  flying  angle,  it  is  at  the 
center,  or  at  a  point  midway  between  the  mar- 
gins. 

PLANE  MONSTROSITIES. — Growing  out  of  the  idea 
that  the  wing  in  nature  must  be  faithfully  copied, 
it  is  believed  by  many  that  a  plane  with  a  pro- 


THE  LIFTING  SURFACES  81 

nounced  thickness  at  its  forward  margin  is  one 
of  the  secrets  of  bird  flight. 
Accordingly   certain   inventors   have  designed 


center^  of 

types  of  wings  which  are  shown  in  Figs.  28  and 
29. 
Both  of  these  types  have  pronounced  bulges,  de- 


signed  to  "split"  the  air,  forgetting,  apparently, 
that  in  other  parts  of  the  machine  every  effort  is 
made  to  prevent  head  resistance. 


82  AEROPLANES 

THE  BIKD  WING  STKUCTUKE. — The  advocates  of 
such  construction  maintain  that  the  forward  edge 
of  the  plane  must  forcibly  drive  the  air  column 
apart,  because  the  bird  wing  is  so  made,  and  that 
while  it  may  not  appear  exactly  logical,  still  there 
is  something  about  it  which  seems  to  do  the  work, 
and  for  that  reason  it  is  largely  adopted. 

WHY  THE  BIED'S  WING  HAS  A  PRONOUNCED 
BULGE. — Let  us  examine  this  claim.  The  bone 
which  supports  the  entire  wing  surface,  called  the 
pectoral,  has  a  heavy  duty  to  perform.  It  is  so 
constructed  that  it  must  withstand  an  extraor- 
dinary torsional  strain,  being  located  at  the  for- 
ward portion  of  the  wing  surface.  Torsion  has 
reference  to  a  twisting  motion. 

In  some  cases,  as  in  the  bat,  this  primary  bone 
has  an  attachment  to  the  rear  of  the  main  joint, 
where  the  rear  margin  of  the  wing  is  attached  to 
the  leg  of  the  animal,  thus  giving  it  a  support 
and  the  main  bone  is,  therefore,  relieved  of  this 
torsional  stress. 

THE  BAT  's  WING. — An  examination  of  the  bat 's 
wing  shows  that  the  pectoral  bone  is  very  small 
and  thin,  thus  proving  that  when  the  entire  wing 
support  is  thrown  upon  the  primary  bone  it  must 
be  large  enough  to  enable  it  to  carry  out  its  func- 
tions. It  is  certainly  not  so  made  because  it  is  a 
necessary  shape  which  best  adapts  it  for  flying. 


THE  LIFTING  SURFACES  83 

If  such  were  the  case  then  nature  erred  in  the 
case  of  the  bat,  and  it  made  a  mistake  in  the 
housefly's  wing  which  has  no  such  anterior  en- 
largement to  assist  (?)  it  in  flying. 

AN  ABNORMAL  SHAPE. — Another  illustration  is 
shown  in  Fig.  30,  which  has  a  deep  concave  di- 
rectly behind  the  forward  margin,  as  at  A,  so 
that  when  the  plane  is  at  an  angle  of  about  22 


degrees,  a  horizontal  line,  as  B,  passing  back  from 
the  nose,  touches  the  incurved  surface  of  the  plane 
at  a  point  about  one-third  of  its  measurement 
back  across  the  plane. 

This  form  is  an  exact  copy  of  the  wing  of  an 
actual  bird,  but  it  belongs,  not  to  the  soaring, 
but  to  the  class  which  depends  on  flapping  wings, 
and  as  such  it  cannot  be  understood  why  it  should 
be  used  for  soaring  machines,  as  all  aeroplanes 
are. 


84  AEROPLANES 

The  foregoing  instances  of  construction  are 
cited  to  show  how  wildly  the  imagination  will 
roam  when  it  follows  wrong  ideals. 

THE  TAIL  AS  A  MONITOR. — The  tendency"  of  the 
center  of  pressure  to  change  necessitates  a  correc- 
tional means,  which  is  supplied  in  the  tail  of 
the  machine,  just  as  the  tail  of  a  kite  serves  to 
hold  it  at  a  correct  angle  with  respect  to  the  wind 
and  the  pull  of  the  supporting  string. 


CHAPTER  VH 

ABNORMAL,   FLYING   STUNTS  AND   SPEEDS 

"PEQUOD,  a  Frenchman,  yesterday  repeatedly 
performed  the  remarkable  feat  of  flying  with  the 
machine  upside  down.  This  exhibition  shows 
that  the  age  of  perfection  has  arrived  in  flying 
machines,  and  that  stability  is  an  accomplished 
fact." — News  item. 

This  is  quoted  to  show  how  little  the  general 
public  knows  of  the  subject  of  aviation.  It  cor- 
rectly represents  the  achievement  of  the  aviator, 
and  it  probably  voiced  the  sentiment  of  many 
scientific  men,  as  well  as  of  the  great  majority  of 
aviators. 

A  few  days  afterwards,  the  same  newspaper 
published  the  following: 

"Lieutenant ,  while  experimenting  yester- 
day morning,  met  his  death  by  the  overturning 
of  his  machine  at  an  altitude  of  300  meters. 
Death  was  instantaneous,  and  the  machine  was 
completely  destroyed. '  * 

85 


86  AEROPLANES 

The  machines  used  by  the  two  men  were  of  the 
same  manufacture,  as  Pequod  used  a  stock  ma- 
chine which  was  strongly  braced  to  support  the 
inverted  weight,  but  otherwise  it  was  not  unlike 
the  well  known  type  of  monoplane. 

Beachy  has  since  repeated  the  experiment  with 
a  bi-plane,  and  it  is  a  feat  which  has  many  imi- 
tators, and  while  those  remarkable  exhibitions 
are  going  on,  one  catastrophe  follows  the  other 
with  the  same  regularity  as  in  the  past. 

Let  us  consider  this  phase  of  flying.  Are  they 
of  any  value,  and  wherein  do  they  teach  anything 
that  may  be  utilized? 

LACK  OF  IMPROVEMENTS  IN  MACHINES. — It  is  re- 
markable that  not  one  single  forward  step  has 
been  taken  to  improve  the  type  of  flying  machines 
for  the  past  five  years.  They  possess  the  same 
shape,  their  stabilizing  qualities  and  mechanism 
for  assuring  stability  are  still  the  same. 

MEN  EXPLOITED,  AND  NOT  THE  MACHINE. — The 
fact  is,  that  during  this  period  the  man  has  been 
exploited  and  not  the  machine.  Men  have  learned, 
some  few  of  them,  to  perform  peculiar  stunts, 
such  as  looping  the  loop,  the  side  glide,  the  drop, 
and  other  features,  which  look,  and  are,  hazardous, 
all  of  which  pander  to  the  sentiments  of  the  spec- 
tators. 


FLYING  STUNTS  AND  SPEEDS        87 

ABNORMAL  FLYING  OF  NO  VALUE. — It  would  be 
too  broad  an  assertion  to  say  that  it  lias  abso- 
lutely no  value,  because  everything  has  its  use 
in  a  certain  sense,  but  if  we  are  to  judge  from 
the  progress  of  inventions  in  other  directions, 
such  exhibitions  will  not  improve  the  art  of  build- 
ing the  device,  or  make  a  fool-proof  machine. 

Indeed,  it  is  the  very  thing  which  serves  as  a 
deterrent,  rather  than  an  incentive.  If  machines 
can  be  handled  in  such  a  remarkable  manner,  they 
must  be,  indeed,  perfect!  Nothing  more  is 
needed!  They  must  represent  the  highest  struc- 
tural type  of  mechanism! 

That  is  the  idea  sought  to  be  conveyed  in  the 
first  paragraph  quoted.  It  is  pernicious,  instead 
of  praiseworthy,  because  it  gives  a  false  impres- 
sion, and  it  is  remarkable  that  even  certain  scien- 
tific journals  have  gravely  discussed  the  per- 
fected ( 1)  type  of  flying  machine  as  demonstrated 
by  the  experiments  alluded  to. 

THE  ART  or  JUGGLING. — We  may,  occasionally, 
see  a  cyclist  who  understands  the  art  of  balancing 
so  well  that  he  can,  with  ease,  ride  a  machine 
which  has  only  a  single  wheel;  or  he  can,  with  a 
stock  bicycle,  ride  it  in  every  conceivable  attitude, 
and  make  it  perform  all  sorts  of  feats. 

It  merely  shows  that  man  has  become  an  ex- 


88  AEROPLANES 

pert  at  juggling  with  a  machine,  the  same  as  he 
manipulates  balls,  and  wheels,  and  other  artifices, 
by  his  dexterity. 

PRACTICAL  USES  THE  BEST  TEST. — The  bicycle 
did  not  require  such  displays  to  bring  it  to  per- 
fection. It  has  been  the  history  of  every  inven- 
tion that  improvements  were  brought  about,  not 
by  abnormal  experiments,  but  by  practical  uses 
and  by  normal  developments. 

The  ability  of  an  aviator  to  fly  with  the  machine 
in  an  inverted  position  is  no  test  of  the  machine's 
stability,  nor  does  it  in  any  manner  prove  that 
it  is  correctly  built.  It  is  simply  and  solely  a 
juggling  feat — something  in  the  capacity  of  a  cer- 
tain man  to  perform,  and  attract  attention  be- 
cause they  are  out  of  the  ordinary. 

CONCAVED  AND  CONVEX  PLANES. — They  were  per- 
formed as  exhibition  features,  and  intended  as 
such,  and  none  of  the  exponents  of  that  kind  of 
flying  have  the  effrontery  to  claim  that  they  prove 
anything  of  value  in  the  machine  itself,  except 
that  it  incidentally  has  destroyed  the  largely 
vaunted  claim  that  concaved  wings  for  supporting 
surfaces  are  necessary. 

How  MOMENTUM  is  A  FACTOR  IN  INVERTED  FLY- 
ING.— When  flying  "upside  down,"  the  convex 
side  of  the  plane  takes  the  pressure  of  the  air, 
and  maintains,  so  it  is  asserted,  the  weight  of  the 


FLYING  STUNTS  AND  SPEEDS        89 

machine.  This  is  true  during  that  period  when 
the  loop  is  being  made.  The  evolution  is  made 
by  first  darting  down,  as  shown  in  Fig.  31,  from 
the  horizontal  position,  1,  to  the  position  2,  where 
the  turn  begins. 


THE  TURNING  MOVEMENT. — Now  note  the  char- 
acteristic angles  of  the  tail,  which  is  the  con- 
trolling factor.  In  position  1  the  tail  is  prac- 
tically horizontal.  In  fact,  in  all  machines,  at 
high  flight,  the  tail  is  elevated  so  as  to  give  little 
positive  angle  of  incidence  to  the  supporting 
planes. 


90  AEROPLANES 

In  position  No.  2,  the  tail  is  turned  to  an  angle 
of  incidence  to  make  the  downward  plunge,  and 
when  the  machine  has  assumed  the  vertical,  as  in 
position  3,  the  tail  is  again  reversed  to  assume 
the  angle,  as  in  1,  when  flying  horizontally. 

At  the  lower  turn,  position  4,  the  tail  is  turned 
similar  to  the  angle  of  position  2,  which  throws 
the  rear  end  of  the  machine  down,  and  as  the 
horizontal  line  of  flight  is  resumed,  in  an  inverted 
position,  as  in  position  4,  the  tail  has  the  same 
angle,  with  relation  to  the  frame,  as  the  support- 
ing planes. 

During  this  evolution  the  engine  is  running,  and 
the  downward  plunge  developes  a  tremendous 
speed,  and  the  great  momentum  thus  acquired, 
together  with  the  pulling  power  of  the  propeller 
while  thus  in  flight,  is  sufficient  to  propel  it  along 
horizontally,  whatever  the  plane  surface  curve,  or 
formation  may  be. 

It  is  the  momentum  which  sustains  it  in  space, 
not  the  air  pressure  beneath  the  wings,  for 
reasons  which  we  have  heretofore  explained. 
Flights  of  sufficient  duration  have  thus  been  made 
to  prove  that  convex,  as  well  as  concave  surfaces 
are  efficient;  nevertheless,  in  its  proper  place  we 
have  given  an  exposition  of  the  reasoning  which 
led  to  the  adoption  of  the  concaved  supporting 
surfaces. 


FLYING  STUNTS  AND  SPEEDS        91 

WHEN  CONCAVED  PLANES  ABE  DESIRABLE. — Un- 
questionably, for  slow  speeds  the  concaved  wing 
is  desirable,  as  will  be  explained,  but  for  high 
speeds,  surface  formation  has  no  value.  That  is 
shown  by  Pequod's  feat. 

THE  SPEED  MANIA. — This  is  a  type  of  mania 
which  pervades  every  field  of  activity  in  the  build- 
ing of  aeroplanes.  Speed  contests  are  of  more 
importance  to  the  spectators  on  exhibition 
grounds  than  stability  or  durability.  Builders 
pander  to  this,  hence  machines  are  built  on  lines 
which  disregard  every  consideration  of  safety 
while  at  normal  flight. 

USES  OF  FLYING  MACHINES. — The  machine  as 
now  constructed  is  of  little  use  commercially. 
Within  certain  limitations  it  is  valuable  for  scout- 
ing purposes,  and  attempts  have  been  made  to 
use  it  commercially.  But  the  unreliable  character 
of  its  performances,  due  to  the  many  elements 
which  are  necessary  to  its  proper  working,  have 
operated  against  it. 

PERFECTION  IN  MACHINES  MUST  COME  BEFORE 
SPEED. — Contrary  to  every  precept  in  the  build- 
ing of  a  new  article,  the  attempt  is  made  to  make 
a  machine  with  high  speed,  which,  in  the  very 
nature  of  things,  operates  against  its  improve- 
ment. The  opposite — lack  of  speed — is  of  far 
greater  utility  at  this  stage  of  its  development. 


92  AEROPLANES 

THE  RANGE  OF  ITS  USE. — The  subject  might  be 
illustrated  by  assuming  that  we  have  a  line  run- 
ning from  A  to  Z,  which  indicates  the  range  of 
speeds  in  aeroplanes.  The  limits  of  speeds  are 
fairly  stated  as  being  within  thirty  and  eighty- 
five  miles  per  hour.  Less  than  thirty  miles  are 
impossible  with  any  type  of  plane,  and  while  some 
have  made  higher  speeds  than  eighty-five  miles  it 
may  be  safe  to  assume  that  such  flights  took  place 
under  conditions  where  the  wind  contributed  to 
the  movement. 


Mile  ft   per  /foitr 


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Pat-fiat  Xr/orv/cdoc, 


CAart  6/tou>tj{$  Aa/wc  of  (tee* 

COMMERCIAL  UTILITY. — Before  machines  can  be 
used  successfully  they  must  be  able  to  attain 
slower  speeds.  Alighting  is  the  danger  factor. 
Speed  machines  are  dangerous,  not  in  flight  or 
at  high  speeds,  but  when  attempting  to  land.  A 
large  plane  surface  is  incompatible  with  speed, 
which  is  another  illustration  that  at  high  veloci- 
ties supporting  surfaces  are  not  necessary. 

Commercial  uses  require  safety  as  the  first  ele- 


FLYING  STUNTS  AND  SPEEDS        93 

ment,  and  reliability  as  the  next  essential.  For 
passenger  service  there  must  be  an  assurance  that 
it  will  not  overturn,  or  that  in  landing  danger  is 
not  ever-present.  For  the  carrying  of  freight  in- 
terrupted service  will  militate  against  it. 

How  few  are  the  attempts  to  solve  the  problem 
of  decreased  speed,  and  what  an  eager,  restless 
campaign  is  being  waged  to  go  faster  and  faster, 
and  the  addition  of  every  mile  above  the  record 
is  hailed  as  another  illustration  of  the  perfection 
(?)  of  the  flying  machine. 

To  be  able  to  navigate  a  machine  at  ten,  or  fif- 
teen miles  an  hour,  would  scarcely  be  interesting 
enough  to  merit  a  paragraph ;  but  such  an  accom- 
plishment would  be  of  far  more  value  than  all  of 
Pequod's  feats,  and  be  more  far-reaching  in  its 
effects  than  a  flight  of  two  hundred  miles  per  hour. 


CHAPTER  VIII 

KITES   AND    GLIDERS 

KITES  are  of  very  ancient  origin,  and  in  China, 
Japan,  and  the  Malayan  Peninsula,  they  have  been 
used  for  many  years  as  toys,  and  for  the  purposes 
of  exhibiting  forms  of  men,  animals,  and  particu- 
larly dragons,  in  their  periodical  displays. 

THE  DRAGON  KITE. — The  most  noted  of  all  are 
the  dragon  kites,  many  of  them  over  a  hundred 
feet  in  length,  are  adapted  to  sail  along  majes- 
tically, their  sinuous  or  snake-like  motions  lending 
an  idea  of  reality  to  their  gorgeously-colored  ap- 
pearance in  flight. 

ITS  CONSTRUCTION. — It  is  very  curiously 
wrought,  and  as  it  must  be  extremely  light,  bam- 
boo and  rattan  are  almost  wholly  used,  together 
with  rice  paper,  in  its  construction. 

Fig.  33  shows  one  form  of  the  arrangement,  in 
which  the  bamboo  rib,  A,  in  which  only  two  sec- 
tions are  shown,  as  B,  B,  form  the  backbone,  and 
these  sections  are  secured  together  with  pivot 
pins  C.  Each  section  has  attached  thereto  a 
hoop,  or  circularly-formed  rib,  D,  the  rib  passing 
through  the  section  B,  and  these  ribs  are  con- 


KITES  AND  GLIDEKS  95 

nected  together  loosely  by  cords  E,  which  run 
from  one  to  the  other,  as  shown. 

These  circular  ribs,  D,  are  designed  to  carry  a 
plurality  of  light  paper  disks,  F,  which  are  at- 
tached .at  intervals,  and  they  are  placed  at  such 
angles  that  they  serve  as  small  wing  surfaces  or 
aeroplanes  to  hold  the  structure  in  flight. 


THE  MALAY  KITE. — The  Malay  kite,  of  which 
Fig.  34  shows  the  structure,  is  merely  made  up  of 
two  cross  sticks,  A,  B,  the  vertical  strip,  A,  being 
bent  and  rigid,  whereas  the  cross  stick,  B,  is  light 
and  yielding,  so  that  when  in  flight  it  will  bend, 
as  shown,  and  as  a  result  it  has  wonderful  sta- 
bility due  to  the  dihedral  angles  of  the  two  sur- 


96 


AEROPLANES 


faces.    This  kite  requires  no  tail  to  give  it  sta- 
bility. 


F'lff.  <#£  77a?  Malay 

DIHEDRAL  ANGLES. — This  is  a  term  to  designate 
a  form  of  disposing  of  the  wings  which  has  been 
found  of  great  service  in  the  single  plane  ma- 
chines. A  plane  which  is  disposed  at  a  rising 


angle,  as  A,  A,  Fig.  35,  above  the  horizontal  line, 
is  called  dihedral,  or  diedral. 

This   arrangement   in  monoplanes   does   away 
with  the  necessity  of  warping  the  planes,  or  chang- 


KITES  AND  GLIDERS  97 

ing  them  while  in  flight.  If,  however,  the  angle 
is  too  great,  the  wind  from  either  quarter  is  liable 
to  raise  the  side  that  is  exposed. 

THE  COMMON  KITE. — While  the  Malay  kite  has 
only  two  points  of  cord  attachment,  both  along 
the  vertical  rib,  the  common  kite,  as  shown  in 
Fig.  36,  has  a  four-point  connection,  to  which  the 


flying  cord  is  attached.  Since  this  form  has  no 
dihedral  angle,  it  is  necessary  to  supply  a  tail, 
which  thus  serves  to  keep  it  in  equilibrium,  while 
in  flight. 

Various  modifications  have  grown  out  of  the 
Malay  kite.  One  of  these  forms,  designed  by 
Eddy,  is  exactly  like  the  Malay  structure,  but  in- 
stead of  having  a  light  flexible  cross  piece,  it  is 
bent  to  resemble  a  bow,  so  that  it  is  rigidly  held 


98 


AEROPLANES 


in  a  bent  position,  instead  of  permitting  the  wind 
to  give  it  the  dihedral  angle. 

THE  Bow  KITE. — Among  the  different  types  are 


&exago)icd  Kite. 

the  bow  kite,  Fig.  37,  and  the  sexagonal  structure, 
Fig.  38,  the  latter  form  affording  an  especially 
large  surface. 


KITES  AND  GLIDERS  99 

THE  Box  KITE. — The  most  marked  improve- 
ment in  the  form* of  kites  was  made  by  Hargreaves, 
in  1885,  and  called  the  box  kite.  It  has  wonderful 
stability,  and  its  use,  with  certain  modifications, 
in  Weather  Bureau  experiments,  have  proven  its 
value. 

It  is  made  in  the  form  of  two  boxes,  A,  B,  open 
at  the  ends,  which  are  secured  together  by  means 
of  longitudinal  bars,  C,  that  extends  from  one  to 
the  other,  so  that  they  are  held  apart  a  distance, 


approximately,  equal  to  the  length  of  one  of  the 
boxes. 

Their  fore  and  aft  stability  is  so  perfect  that 
the  flying  cord  D  is  attached  at  one  point  only, 
and  the  sides  of  the  boxes  provide  lateral  sta- 
bility to  a  marked  degree. 

THE  VOISON  BIPLANE. — This  kind  of  kite  fur- 
nished the  suggestion  for  the  Voison  biplane, 
which  was  one  of  the  earlier  productions  in  flying 
machines. 


100  AEROPLANES 

Fig.  40  shows  a  perspective  of  the  Voison  plane, 
which  has  vertical  planes  A,  A,  at  the  ends,  and 
also  intermediate  curtains  B,  B.  This  was  found 
to  be  remarkably  stable,  but  during  its  turning 
movements,  or  in  high  winds,  was  not  satisfactory, 
and  for  that  reason  was  finally  abandoned. 

LATERAL  STABILITY  IN  KITES  NOT  CONCLUSIVE  AS 
TO  PLANES. — This  is  instanced  to  show  that  while 
such  a  form  is  admirably  adapted  for  kite  pur- 
poses, where  vertical  curtains  are  always  in  line 


with  the  wind  movement,  and  the  structure  is  held 
taut  by  a  cord,  the  lateral  effect,  when  used  on  a 
machine  which  does  not  at  all  times  move  in  line 
with  the  moving  air  current.  A  condition  is  thus 
set  up  which  destroys  the  usefulness  of  the  box 
kite  formation. 

THE  SPEAR  KITE. — This  is  a  novel  kite,  with 
remarkable  steadiness  and  is  usually  made  with 
the  wings  on  the  rear  end  larger  than  those  on 
the  forward  end  (Fig.  41),  as  thereby  the  cord 


KITES  AND  GLIDERS 


101 


A  can  be  attached  to  the  spear  midway  between 
the  two  sets  of  wings. 


THE  CELLULAR  KITE. — Following  out  the  sug- 
gestion of  the  Hargreaves  kite,  numerous  forms 
embodying  the  principle  of  the  box  structure  were 
made  and  put  on  the  market  before  the  aeroplane 
became  a  reality. 


A  structure  of  this  form  is  illustrated  in  Fig. 
42.    Each  box,  as  A,  B,  has  therein  a  plurality  of 


102 


AEROPLANES 


vertical  and  horizontal  partitions,  so  that  a  num- 
ber of  cells  are  provided,  the  two  cell-like  boxes 
being  held  apart  by  a  bar  C,  axially  arranged. 

This  type  is  remarkably  stable,  due  to  the  small 
cells,  and  kites  of  this  kind  are  largely  used  for 
making  scientific  experiments. 

THE  TETRAHEDRAL,  KITE. — Prof.  Bell,  inventor 
of  the  telephone,  gave  a  great  deal  of  study  to 


kites,  which  resulted  in  the  tetrahedral  formation, 
as  shown  in  Fig.  43. 

The  structure,  apparently,  is  somewhat  com- 
plicated, but  an  examination  of  a  single  pair  of 
blades,  as  shown  at  A,  shows  that  it  is  built  up  of 
triangularly-formed  pieces,  and  that  the  openings 
between  the  pieces  are  equal  to  the  latter,  thereby 
providing  a  form  of  kite  which  possesses  equi- 
librium to  a  great  degree. 


KITES  AND  GLIDERS  103 

It  has  never  been  tried  with  power,  and  it  is 
doubtful  whether  it  would  be  successful  as  a  sus- 
taining surface  for  flying  machines,  for  the  same 
reasons  that  caused  failure  with  the  box-like  for- 
mation of  the  Voison  Machine. 

THE  DELTOID. — The  deltoid  is  the  simplest,  and 
the  most  easily  constructed  of  all  the  kites.  It  is 
usually  made  from  stiff  cardboard,  A-shaped  in 


outline,  as  shown  in  Figs.  44  and  45,  and  bent  along 
a  central  line,  as  at  A,  forming  two  wings,  each 
of  which  is  a  right-angled  triangle. 

The  peculiarity  of  this  formation  is,  that  it  has 
remarkable  stability  when  used  as  a  kite,  with 
either  end  foremost.  If  a  small  weight  is  placed 
at  the  pointed  end,  and  it  is  projected  through  the 
air,  it  will  fly  straight,  and  is  but  little  affected 
by  cross  currents. 


104  AEROPLANES 

THE  DUNNE  FLYING  MACHINE. — A  top  view  of 
this  biplane  is  shown  in  Fig.  46.  The  A-shaped 
disposition  of  the  planes,  gives  it  good  lateral 
stability,  but  it  has  the  disadvantage  under  which 
all  aeroplanes  labor,  that  the  entire  body  of  the 
machine  must  move  on  a  fore  and  aft  vertical 
plan  in  order  to  ascend  or  descend. 

flan  Meur 


This  is  a  true  deltoid  formation,  as  the  angle  of 
incidence  of  the  planes  is  so  disposed  that  when 
the  planes  are  horizontal  from  end  to  end,  the  in- 
clination is  such  as  to  make  it  similar  to  the  deltoid 
kite  referred  to. 

EOTATING  KITE. — A  type  of  kite  unlike  the 
others  illustrated  is  a  rotating  structure,  which 
gives  great  stability,  due  to  the  gyroscopic  action 
on  the  supporting  surfaces. 

Fig.  47  shows  a  side  view  with  the  top  in  sec- 
tion. The  supporting  surface  is  umbrella-shaped. 
In  fact,  the  ordinary  umbrella  will  answer  if  not 
dished  too  much.  An  angularly-bent  piece  of  wire 


KITES  AND  GLIDEES  105 

A,  provided  with  loops  B,  B,  at  the  ends,  serve  as 
bearings  for  the  handle  of  the  umbrella. 

At  the  bend  of  the  wire  loop  C,  the  cord  D  is 
attached.  The  lower  side  of  the  umbrella  top  has 
cup-shaped  pockets  E,  near  the  margin,  so  ar- 
ranged that  their  open  ends  project  in  the  same 
direction,  and  the  wind  catching  them  rotates  the 
circular  plane. 


jFZg.  47.  Jlofabte  UmbrdfaXtfa. 

KITE  PKINCIPLES. — A  careful  study  of  the  ex- 
amples here  given,  will  impress  the  novice  with 
one  important  fact,  which,  in  its  effect  has  a  more 
important  bearing  on  successful  flight,  than  all 
the  bird  study  and  speculations  concerning  its 
mysteries. 

This  fact,  in  essence,  is,  that  the  angle  of  the 
kite  is  the  great  factor  in  flight  next  to  the  power 
necessary  to  hold  it.  Aside  from  this,  the  com- 


106  AEROPLANES 

parison  between  kites  and  aeroplanes  is  of  no 
practical  value. 

Disregarding  the  element  of  momentum,  the 
drift  of  a  machine  against  a  wind,  is  the  same, 
dynamically,  as  a  plane  at  rest  with  the  wind 
moving  past  it.  But  there  is  this  pronounced 
difference:  The  cord  which  supports  the  kite 
holds  it  so  that  the  power  is  in  one  direction  only. 

When  a  side  gust  of  wind  strikes  the  kite  it 
is  moved  laterally,  in  sympathy  with  the  kite, 
hence  the  problem  of  lateral  displacement  is  not 
the  same  as  with  the  aeroplane. 

LATEKAL  STABILITY  IN  KITES. — In  the  latter  the 
power  is  definitely  fixed  with  relation  to  the  ma- 
chine itself,  and  if  we  should  assume  that  a  plane 
with  a  power  on  it  sufficient  to  maintain  a  flight 
of  40  miles  an  hour,  should  meet  a  wind  moving 
at  the  same  speed,  the  machine  would  be  station- 
ary in  space. 

Such  a  condition  would  be  the  same,  so  far  as 
the  angles  of  the  planes  are  concerned,  with  a 
kite  held  by  a  string,  but  there  all  similarity  in 
action  ends. 

The  stabilizing  quality  of  the  kite  may  be  per- 
fect, as  the  wind  varies  from  side  to  side,  but  the 
aeroplane,  being  free,  moves  to  the  right  or  to 
the  left,  and  does  not  adjust  itself  by  means  of  a 
fixed  point,  but  by  a  movable  one. 


KITES  AND  GLIDEES  107 

SlMILAEITY    OF    FOEE    AND    AFT    CONTROL. — Fore 

and  aft,  however,  the  kite  and  aeroplane  act  the 
same.  Fig.  48  shows  a  diagram  which  illustrates 
the  forces  which  act  on  the  kite,  and  by  means 
of  which  it  adjusts  its  angle  automatically. 

Let  us  assume  that  the  kite  A  is  flown  from 
a  cord  B,  so  that  its  angle  is  22y2  degrees,  the 


wind  being  15  miles  per  hour  to  maintain  the 
cord  B  at  that  angle.  When  the  wind  increases 
to  20  miles  an  hour  there  is  a  correspondingly 
greater  lift  against  the  kite. 

As  its  angle  is  fixed  by  means  of  the  loop  C, 
it  cannot  change  its  angle  with  reference  to  the 
cord,  or  independently  of  it,  and  its  only  course 
is  to  move  up  higher  and  assume  the  position 


108  AEROPLANES 

shown  by  the  figure  at  D,  and  the  angle  of  in- 
cidence of  the  kite  is  therefore  changed  to  15  de- 
grees, or  even  to  10  degrees. 

In  the  case  of  the  aeroplane  the  effect  is  simi- 
lar from  the  standpoint  of  power  and  disposition 
of  the  planes.  If  it  has  sufficient  power,  and  the 
angle  of  the  planes  is  not  changed,  it  will  ascend ; 
if  the  planes  are  changed  to  15  degrees  to  corre- 
spond with  the  kite  angle  it  will  remain  stationary. 

GLIDING  FLIGHT. — The  earliest  attempt  to  fly 
by  gliding  is  attributed  to  Oliver,  a  Monk*  of 
Malmesbury  who,  in  1065  prepared  artificial 
wings,  and  with  them  jumped  from  a  tower,  being 
injured  in  the  experiment. 

Nearly  700  years  later,  in  1801,  Eesnier,  a 
Frenchman,  conducted  experiments  with  varying 
results,  followed  by  Berblinger,  in  1842,  and 
LeBris,  a  French  sailor,  in  1856. 

In  1884,  J.  J.  Montgomery,  of  California,  de- 
signed a  successful  glider,  and  in  1889  Otto  and 
Gustav  Lilienthal  made  the  most  extended  tests, 
in  Germany,  and  became  experts  in  handling 
gliders. 

Pilcher,  in  England,  was  the  next  to  take  up  the 
subject,  and  in  1893  made  many  successful  glides, 
all  of  the  foregoing  machines  being  single  plane 
surfaces,  similar  to  the  monoplane. 

Long  prior  to  1896  Octave  Chanute,  an  en- 


KITES  AND  GLIDEKS  109 

gineer,  gave  the  subject  much  study,  and  in  that 
year  made  many  remarkable  flights,  developing 
the  double  plane,  now  known  as  the  biplane. 

He  was  an  ardent  believer  in  the  ability  of  man 
to  fly  by  soaring  means,  and  without  using  power 
for  the  purpose. 

It  is  doubtful  whether  gliders  contributed  much 
to  the  art  in  the  direction  of  laterally  stabilizing 
aeroplanes.  They  taught  useful  lessons  with  re- 
spect to  area  and  fore  and  aft  control. 

The  kite  gave  the  first  impulse  to  seek  out  a 
means  for  giving  equilibrium  to  planes,  and 
Montgomery  made  a  kite  with  warping  wings  as 
early  as  1884. 

Penaud,  a  Frenchman,  in  1872,  made  a  model 
aeroplane  which  had  the  stabilizing  means  in  the 
tail.  All  these  grew  out  of  kite  experiments ;  and 
all  gliders  followed  the  kite  construction,  or  the 
principles  involved  in  them,  so  that,  really,  there 
is  but  one  intervening  step  between  the  kite  and 
the  flying  machine,  as  we  know  it,  the  latter  being 
merely  kites  with  power  attached,  as  substitutes 
for  the  cords. 

ONE  OP  THE  USES  OF  GLIDER  EXPERIMENTS. — 
There  is  one  direction  in  which  gliders  are  valu- 
able to  the  boy  and  to  the  novice  who  are  inter- 
ested in  aviation.  He  may  spend  a  lifetime  in 
gliding  and  not  advance  in  the  art.  It  is  ques- 


110  AEROPLANES 

tionable  whether  in  a  scientific  way  it  will  be  of 
any  service  to  him ;  but  experiments  of  this  charac- 
ter give  confidence,  the  ability  to  quickly  grasp 
a  situation,  and  it  will  thus  teach  self  reliance  in 
emergencies. 

When  in  a  glider  quick  thinking  is  necessary. 
The  ability  to  shift  from  one  position  to  another ; 
to  apply  the  weight  where  required  instantane- 
ously ;  to  be  able  during  the  brief  exciting  moment 
of  flight  to  know  just  what  to  do,  requires  alert- 
ness. 

Some  are  so  wedded  to  the  earth  that  slight 
elevation  disturbs  them.  The  sensation  in  a 
glider  while  in  flight  is  unlike  any  other  experience. 
It  is  like  riding  a  lot  of  tense  springs,  and  the 
exhilaration  in  gliding  down  the  side  of  a  hill, 
with  the  feet  free  and  body  suspended,  is  quite 
different  from  riding  in  an  aeroplane  with  power 
attached. 

HINTS  IN  GLIDING. — It  seems  to  be  a  difficult 
matter  to  give  any  advice  in  the  art  of  gliding.  It 
is  a  feat  which  seems  to  necessitate  experiment 
from  first  to  last.  During  the  hundreds  of  tests 
personally  made,  and  after  witnessing  thousands 
of  attempts,  there  seems  to  be  only  a  few  sugges- 
tions or  possible  directions  in  which  caution  might 
be  offered. 

First,  in  respect  to  the  position  of  the  body  at 


KITES  AND  GLIDERS  111 

the  moment  of  launching.  The  glider  is  usually 
so  made  that  in  carrying  it,  preparatory  to  making 
the  run  and  the  leap  required  to  glide,  it  is  held 
so  that  it  balances  in  the  hands. 

Now  the  center  of  air  pressure  in  gliding  may 
not  be  at  the  same  point  as  its  sustaining  weight 
when  held  by  the  hand,  and  furthermore,  as  the 
arm-pits,  by  which  the  body  of  the  experimenter 
are  held  while  gliding,  are  not  at  the  same  point, 
but  to  the  rear  of  the  hands,  the  moment  the  glider 
is  launched  too  great  a  weight  is  brought  to  the 
rear  margin  of  the  planes,  hence  its  forward  end 
lifts  up. 

This  condition  will  soon  manifest  itself,  and  be 
corrected  by  the  experimenter;  but  there  is  an- 
other difficulty  which  is  not  so  easy  to  discover 
and  so  quick  to  remedy,  and  that  is  the  swing  of 
the  legs  the  moment  the  operator  leaves  the 
ground. 

The  experimenter  learns,  after  many  attempts, 
that  gliding  is  a  matter  of  a  few  feet  only,  and  he 
anticipates  landing  too  soon,  and  the  moment  he 
leaps  from  the  ground  the  legs  are  swung  for- 
wardly  ready  to  alight. 

This  is  done  unconsciously,  just  as  a  jumper 
swings  his  legs  forwardly  in  the  act  of  alighting. 
Such  a  motion  naturally  disturbs  the  fore  and  aft 
stability  of  the  gliding  machine,  by  tilting  up  the 


112  AEROPLANES 

forward  margin,  and  it  banks  against  the  air, 
instead  of  gliding. 

The  constant  fear  of  all  gliders  is,  that  the 
machine  will  point  downwardly,  and  his  motion, 
as  well  as  the  position  of  the  body,  tend  to  shoot 
it  upwardly,  instead. 


CHAPTER  IX 

AEROPLANE  CONSTRUCTION 

As  may  be  inferred  from  the  foregoing  state- 
ments, there  are  no  definite  rules  for  the  con- 
struction of  either  type  of  flying  machine,  as  the 
flying  models  vary  to  such  an  extent  that  it  is 
difficult  to  take  either  of  them  as  a  model  to  rep- 
resent the  preferred  type  of  construction. 

LATERAL,  AND  FORE  AND  APT. — The  term  lateral 
should  be  understood,  as  applied  to  aeroplanes. 
It  is  always  used  to  designate  the  direction  at 
right  angles  to  the  movement  of  the  machine. 
Fore  and  aft  is  a  marine  term  meaning  lengthwise, 
or  from  front  to  rear,  hence  is  always  at  right 
angles  to  the  lateral  direction. 

The  term  transverse  is  equivalent  to  lateral, 
in  flying  machine  parlance,  but  there  is  this  dis- 
tinction :  Transverse  has  reference  to  a  machine 
or  object  which,  like  the  main  planes  of  an  aero- 
plane, are  broader,  (that  is, — from  end  to  end) 
than  their  length,  (from  front  to  rear). 

On  the  other  hand,  lateral  has  reference  to  side 
branches,  as,  for  instance,  the  monoplane  wings, 

113 


114  AEROPLANES 

which  branch  out  from  the  sides  of  the  fore  and 
aft  body. 

STABILITY  AND  STABILIZATION. — These  terms  con- 
stantly appear  in  describing  machines  and  their 
operations.  If  the  flying  structure,  whatever  it 
may  be,  has  means  whereby  it  is  kept  from  rocking 
from  side  to  side,  it  has  stability,  which  is  usually 
designated  as  lateral  stability.  The  mechanism 
for  doing  this  is  called  a  stabilizer. 

THE  WEIGHT  SYSTEM. — The  Wright  machine  has 
reference  solely  to  the  matter  of  laterally  con- 
trolling the  flying  structure,  and  does  not  pertain 
to  the  form  or  shape  of  the  planes. 

In  Fig.  49  A  designates  the  upper  and  lower 
planes  of  a  Wright  machine,  with  the  peculiar 
rounded  ends.  The  ends  of  the  planes  are  so 
arranged  that  the  rear  margins  may  be  raised  or 
lowered,  independently  of  the  other  portions  of 
the  planes,  which  are  rigid.  This  movement  is 
indicated  in  sketch  1,  where  the  movable  part  B 
is,  as  we  might  say,  hinged  along  the  line  C. 

The  dotted  line  D  on  the  right  hand  end,  shows 
how  the  section  is  depressed,  while  the  dotted 
lines  E  at  the  left  hand  end  shows  the  section 
raised.  It  is  obvious  that  the  downturned  ends, 
as  at  D,  will  give  a  positive  angle  at  one  end  of  the 
planes,  and  the  upturned  wings  E  at  the  other  end 
will  give  a  negative  angle,  and  thus  cause  the  right 


AEROPLANE  CONSTRUCTION       115 


116  AEROPLANES 

hand  end  to  raise,  and  the  other  end  to  move 
downwardly,  as  the  machine  moves  forwardly 
through  the  air. 

CONTROLLING  THE  WABPING  ENDS. — Originally 
the  Wrights  controlled  these  warping  sections  by 
means  of  a  cradle  occupied  by  the  aviator,  so  tjiat 
the  cradle  would  move  or  rock,  dependent  on  the 
tilt  of  the  machine.  This  was  what  was  termed 
automatic  control.  This  was  found  to  be  unsatis- 
factory, and  the  control  has  now  been  placed  so 
that  it  connects  with  a  lever  and  is  operated  by 
the  aviator,  and  is  called  Manually-operated  con- 
trol. 

In  all  forms  of  control  the  wings  on  one  side  are 
depressed  on  one  side  and  correspondingly  ele- 
vated on  the  other. 

THE  CUKTIS  WINGS. — Curtis  has  small  wings, 
or  ailerons,  intermediate  the  supporting  surfaces, 
and  at  their  extremities,  as  shown  in  sketch  2. 
These  are  controlled  by  a  shoulder  rack  or  swing- 
ing frame  operated  by  the  driver,  so  that  the  body 
in  swinging  laterally  will  change  the  two  wings 
at  the  same  time,  but  with  angles  in  different 
directions. 

THE  FARMAN  AILERONS. — Farman's  disposition 
is  somewhat  different,  as  shown  in  sketch  3.  The 
wings  are  hinged  to  the  upper  planes  at  their  rear 
edges,  and  near  the  extremities  of  the  planes. 


AEROPLANE  CONSTEUCTION       117 

Operating  wires  lead  to  a  lever  within  reach  of  the 
aviator,  and,  by  this  means,  the  wings  are  held  at 
any  desired  angle,  or  changed  at  will. 

The  difficulty  of  using  any  particular  model,  is 
true,  also,  of  the  arrangement  of  the  fore  and  aft 
control,  as  well  as  the  means  for  laterally  stabiliz- 
ing it.  In  view  of  this  we  shall  submit  a  general 
form,  which  may  be  departed  from  at  will. 

FEATURES  WELL  DEVELOPED. — Certain  features 
are  fairly  well  developed,  however.  One  is  the 
angle  of  the  supporting  plane,  with  reference  to 
the  frame  itself;  and  the  other  is  the  height  at 
which  the  tail  and  rudder  should  be  placed  above 
the  surface  of  the  ground  when  the  machine  is  at 
rest. 

DEPRESSING  THE  BEAR  END. — This  latter  is  a 
matter  which  must  be  taken  into  consideration, 
because  in  initiating  flight  the  rear  end  of  the 
frame  is  depressed  in  order  to  give  a  sufficient 
angle  to  the  supporting  planes  so  as  to  be  able  to 
inaugurate  flight. 

In  order  to  commence  building  we  should  have 
some  definite  idea  with  respect  to  the  power,  as 
this  will,  in  a  measure,  determine  the  area  of  the 
supporting  surfaces,  as  a  whole,  and  from  this 
the  sizes  of  the  different  planes  may  be  determined. 

DETERMINING  THE  SIZE. — Suppose  we  decide  on 
300  square  feet  of  sustaining  surface.  This  may 


118  AEKOPLANES 

require  a  30,  a  40  or  a  50  horse  power  motor, 
dependent  on  the  speed  required,  and  much  higher 
power  has  been  used  on  that  area. 

However,  let  us  assume  that  a  forty  horse  power 
motor  is  available,  our  300  square  feet  of  surface 
may  be  put  into  two  planes,  each  having  150  square 
feet  of  surface,  which  would  make  each  5'  by  30' 
in  size ;  or,  it  may  be  decided  to  make  the  plane  si 
narrower,  and  proportionally  longer.  This  is  im- 
material. The  shorter  the  planes  transversely, 
the  greater  will  be  the  stability,  and  the  wider  the 
planes  the  less  will  be  the  lift,  comparatively. 

EULE  FOE  PLACING  THE  PLANES. — The  rule  for 
placing  the  planes  is  to  place  them  apart  a  dis- 
tance equal  to  the  width  of  the  planes  themselves, 
so  that  if  we  decide  on  making  them  five  feet  wide, 
they  should  be  placed  at  least  five  feet  apart. 
This  rule,  while  it  is  an  admirable  one  for  slow 
movements  or  when  starting  flight,  is  not  of  any 
advantage  while  in  rapid  flight. 

If  the  machine  is  made  with  front  and  rear 
horizontally-disposed  rudders,  or  elevators,  they 
also  serve  as  sustaining  surfaces,  which,  for  the 
present  will  be  disregarded. 

Lay  off  a  square  A,  Fig.  49a,  in  which  the  ver- 
tical lines  B,  B,  and  the  horizontal  lines  C,  C,  are 
5'  long,  and  draw  a  cross  D  within  this,  the  lines 
running  diagonally  from  the  corners. 


AEROPLANE  CONSTRUCTION       119 


Now  step  off  from  the  center  cross  line  D,  three 
spaces,  each  five  fe-et  long,  to  a  point  E,  and  join 
this  point  by  means  of  upper  and  lower  bars  F, 


Sacin  PlcgM&. 


Gr,  with  the  upper  and  lower  planes,  so  as  to  form 
the  tail  frame. 

As  shown  in  Fig.  50,  the  planes  should  now  be 
indicated,  and  placed  at  an  angle  of  about  8  de- 
grees angle,  which  are  illustrated,  H  being  the 


of  Control  PZanez. 


upper  and  I  the  lower  plane.  Midway  between  the 
forward  edges  of  the  two  planes,  is  a  horizontal 
line  J,  extending  forwardly,  and  by  stepping  off 
the  width  of  two  planes,  a  point  K  is  made,  which 
forms  the  apex  of  a  frame  L,  the  rear  ends  of  the 


120 


AEROPLANES 


AEROPLANE  CONSTRUCTION        121 

bars  being  attached  to  the  respective  planes  H,  I, 
at  their  forward  edges. 

ELEVATING  PLANES. — We  must  now  have  the  gen- 
eral side  elevation  of  the  frame,  the  planes,  their 
angles,  the  tail  and  the  mdder  support,  and  the 
frame  for  the  forward  elevator. 

To  this  may  be  added  the  forward  elevating 
plane  L,  the  rear  elevator,  or  tail  M,  and  the  ver- 
tical steering  rudder  N. 

The  frame  which  supports  the  structure  thus 
described,  may  be  made  in  a  variety  of  ways,  the 
object  being  to  provide  a  resilient  connection  for 
the  rear  wheel  0. 

Fig.  52  shows  a  frame  which  is  simple  in  con- 
struction and  easily  attached.  The  lower  fore 
and  aft  side  bars  P  have  the  single  front  wheel 
axle  at  the  forward  end,  and  the  aft  double  wheels 
at  the  rear  end,  a  flexible  bar  Q,  running  from  the 
rear  wheel  axle  to  the  forward  end  of  the  lower 
plane. 

A  compression  spring  R  is  also  mounted  be- 
tween the  bar  and  rear  end  of  the  lower  plane  to 
take  the  shock  of  landing.  The  forward  end  of 
the  bar  P  has  a  brace  S  extending  up  to  the  front 
edge  of  the  lower  plane,  and  another  brace  T  con- 
nects the  bars  P,  S,  with  the  end  of  the  forwardly- 
pr ejecting  frame. 

The  full  page  view,  Fig.  53,  represents  a  plan 


122 


AEROPLANES 


AEROPLANE  CONSTEUCTION        123 

view,  with  one  of  the  wings  cut  away,  showing  the 
general  arrangement  of  the  frame,  and  the  three 
wheels  required  for  support,  together  with  the 
brace  bars  referred  to. 

The  necessity  of  the  rear  end  elevation  will 
now  be  referred  to.  The  tail  need  not,  neces- 
sarily, be  located  at  a  point  on  a  horizontal  line 
between  the  planes.  It  may  be  higher,  or  lower 
than  the  planes,  but  it  should  not  be  in  a  position 


to  touch  the  ground  when  the  machine  is  about 
to  ascend. 

The  angle  of  ascension  in  the  planes  need  not 
exceed  25  degrees  so  the  frame  does  not  require 
an  angle  of  more  than  17  degrees.  This  is  shown 
in  Fig.  54,  where  the  machine  is  in  a  position 
ready  to  take  the  air  at  that  angle,  leaving  ample 
room  for  the  steering  rudder. 

ACTION  IN  ALIGHTING. — Also,  in  alighting,  the 
machine  is  banked,  practically  in  the  same  posi- 


124  AEROPLANES 

tion  thus  shown,  so  that  it  alights  on  the  rear 
wheels  0. 

The  motor  U  is  usually  mounted  so  its  shaft  is 
midway  between  the  planes,  the  propeller  V  being 
connected  directly  with  the  shaft,  and  being  be- 
hind the  planes,  is  on  a  medial  line  with  the 
machine. 

The  control  planes  L,  M,  N,  are  all  connected  up 
by  means  of  flexible  wires  with  the  aviator  at  the 
set  W,  the  attachments  being  of  such  a  character 
that  their  arrangement  will  readily  suggest  them- 
selves to  the  novice. 

THE  MONOPLANE. — From  a  spectacular  stand- 
point a  monoplane  is  the  ideal  flying  machine.  It 
is  graceful-  in  outline,  and  from  the  fact  that  it 
closely  approaches  the  form  of  the  natural  flyer, 
seems  to  be  best  adapted  as  a  type,  compared  with 
the  biplane. 

THE  COMMON  FLY. — So  many  birds  have  been 
cited  in  support  of  the  various  flying  theories  that 
the  house  fly,  as  an  example  has  been  disregarded. 
We  are  prone  to  overlook  the  small  insect,  but  it 
is,  nevertheless,  a  sample  which  is  just  as  potent 
to  show  the  efficiency  of  wing  surface  as  the  con- 
dor or  the  vulture. 

The  fly  has  greater  mobility  than  any  other  fly- 
ing creature.  By  the  combined  action  of  its  legs 
and  wings  it  can  spring  eighteen  inches  in  the 


AEEOPLANE  CONSTRUCTION       125 

tenth  of  a  second ;  and  when  in  flight  can  change 
its  course  instantaneously. 

If  a  sparrow  had  the  same  dexterity,  propor- 
tionally, it  could  make  a  flight  of  800  feet  in  the 
same  time.  The  posterior  legs  of  the  fly  are  the 


same  length  as  its  body,  which  enable  it  to  spring 
from  its  perch  with  amazing  facility. 

The  wing  surface,  proportioned  to  its  body  and 
weight,  is  no  less  a  matter  for  wonder  and  con- 
sideration. 


126  AEEOPLANES 

In  Fig.  55  is  shown  the  outlines  of  the  fly  with 
outstretched  wings.  Fig.  56  represents  it  with 
the  wing  folded,  and  Fig.  57  is  a  view  of  a  wing 
with  the  relative  size  of  the  top  of  the  body  shown 
in  dotted  lines. 


The  first  thing  that  must  attract  attention,  after 
a  careful  study  is  the  relative  size  of  the  body 
and  wing  surface.  Each  wing  is  slightly  smaller 
than  the  upper  surface  of  the  body,  and  the  thick- 
ness of  the  body  is  equal  to  each  wing  spread. 


i*fee  ofwinG  aftcl  frxfy* 


The  weight,  compared  with  sustaining  surface, 
if  expressed  in  understandable  terms,  would  be 
equal  to  sixty  pounds  for  every  square  foot  of  sur- 
face. 

STREAM  LINES. — The  next  observation  is,  that 
what  are  called  stream  lines  do  not  exist  in  the  fly. 
Its  head  is  as  large  in  cross  section  as  its  body, 


AEROPLANE  CONSTEUCTION        127 

with  the  slightest  suggestion  only,  of  a  pointed 
end.  Its  wings  are  perfectly  flat,  forming  a  true 
plane,  not  dished,  or  provided  with  a  cambre,  even, 
that  upward  curve,  or  bulge  on  the  top  of  the  aero- 
plane surface,  which  seems  to  possess  such  a  fas- 
cination for  many  bird  flight  advocates. 

It  will  also  be  observed  that  the  wing  connec- 
tion with  the  body  is  forward  of  the  line  A,  which 
represents  the  point  at  which  the  body  will  bal- 
ance itself,  and  this  line  passes  through  the  wings 
so  that  there  is  an  equal  amount  of  supporting 
surface  fore  and  aft  of  the  line. 

Again,  the  wing  attachment  is  at  the  upper  side 
of  the  body,  and  the  vertical  dimension  of  the 
body,  or  its  thickness,  is  equal  to  four-fifths  of  the 
length  of  he  wing. 

The  wing  socket  permits  a  motion  similar  to  a 
universal  joint,  Fig.  55  showing  how  the  inner 
end  of  the  wing  has  a  downward  bend  where  it 
joins  the  back,  as  at  B. 

THE  MONOPLANE  FORM. — For  the  purpose  of 
making  comparisons  the  illustrations  of  the  mono- 
plane show  a  machine  of  300  square  feet  of  sur- 
face, which  necessitates  a  wing  spread  of  forty 
feet  from  tip  to  tip,  so  that  the  general  dimen- 
sions of  each  should  be  IS1/^  feet  by  Sy2  feet  at  its 
widest  point. 

First  draw  a  square  forty  feet  each  way,  as  in 


128 


AEEOPLANES 


Fig.  58,  and  through  this  make  a  horizontal  line 
1,  and  four  intermediate  vertical  lines  are  then 
drawn,  as  2,  3,  4,  5,  thus  providing  five  divisions, 
each  eight  feet  wide.  In  the  first  division  the 
planes  A,  B,  are  placed,  and  the  tail,  or  elevator 
C,  is  one-half  the  width  of  the  last  division. 


Q,  f^an  of  Monoplane. 


The  frame  is  3y2  feet  wide  at  its  forward  end, 
and  tapers  down  to  a  point  at  its  rear  end,  where 
the  vertical  control  plane  D  is  hinged,  and  the 
cross  struts  E,  E}  are  placed  at  the  division  lines 
3,  4,  5. 

The  angles  of  the  planes,  with  relation  to  the 
frame,  are  usually  greater  than  in  the  biplane, 


AEROPLANE  CONSTRUCTION        129 

for  the  reason  that  the  long  tail  plane  requires 
a  greater  angle  to  be  given  to  the  planes  when 
arising;  or,  instead  of  this,  the  planes  A,  B,  are 
mounted  high  enough  to  permit  of  sufficient  angle 
for  initiating  flight  without  injuring  the  tail  D. 

Some  monoplanes  are  built  so  they  have  a  sup- 
port on  wheels  placed  fore  and  aft.  In  others 
the  tail  is  supported  by  curved  skids,  as  shown 
at  A,  Fig.  59,  in  which  case  the  forward  support- 


J!7levatio?i,  Tfto/ioplane. 

ing  wheels  are  located  directly  beneath  the  planes. 

As  the  planes  are  at  about  eighteen  degrees 
angle,  relative  to  the  frame,  and  the  tail  plane 
B  is  at  a  slight  negative  angle  of  incidence,  as 
shown  at  the  time  when  the  engine  is  started,  the 
air  rushing  back  from  the  propeller,  elevates  the 
tail,  and  as  the  machine  moves  forwardly  over 
the  ground,  the  tail  raises  still  higher,  so  as  to 
give  a  less  angle  of  incidence  to  the  planes  while 
skimming  along  the  surface  of  the  ground. 

In  order  to  mount,  the  tail  is  suddenly  turned 


130  AEROPLANES 

to  assume  a  sharp  negative  angle,  thus  swinging 
the  tail  downwardly,  and  this  increases  the  angle 
of  planes  to  such  an  extent  that  the  machine  leaves 
the  ground,  after  which  the  tail  is  brought  to  the 
proper  angle  to  assure  horizontal  flight. 

The  drawing  shows  a  skid  at  the  forward  end, 
attached  to  the  frame  which  carries  the  wheels. 
The  wheels  are  mounted  beneath  springs  so  that 
when  the  machine  alights  the  springs  yield  suf- 
ficiently to  permit  the  skids  to  strike  the  ground, 
and  they,  therefore,  act  as  brakes,  to  prevent  the 
machine  from  traveling  too  far. 


CHAPTER  X 

POWER  AND   ITS   APPLICATION 

THIS  is  a  phase  of  the  flying  machine  which  has 
the  greatest  interest  to  the  boy.  He  instinctively 
sees  the  direction  in  which  the  machine  has  its 
life, — its  moving  principle.  Planes  have  their 
fascination,  and  propellers  their  mysterious  ele- 
ments, but  power  is  the  great  and  absorbing  ques- 
tion with  him. 

We  shall  try  to  make  its  application  plain  in 
the  following  pages.  We  have  nothing  to  do  here 
with  the  construction  and  operation  of  the  motor 
itself,  as,  to  do  that  justice,  would  require  pages. 

FEATURES  IN  POWER  APPLICATION. — It  will  be 
more  directly  to  the  point  to  consider  the  follow- 
ing features  of  the  power  and  its  application: 

1.  The  amount  of  power  necessary. 

2.  How  to  calculate  the  power  applied. 

3.  Its  mounting. 

WHAT  AMOUNT  OP  POWER  is  NECESSARY. — In  the 
consideration  of  any  power  plant  certain  calcula- 
tions must  be  made  to  determine  what  is  required. 
A  horse  power  means  the  lifting  of  a  certain 

131 


132  AEROPLANES 

weight,  a  definite  distance,  within  a  specified 
time. 

If  the  weight  of  the  vehicle,  with  its  load,  are 
known,  and  its  resistance,  or  the  character  of  the 
roadway  is  understood,  it  is  a  comparatively  easy 
matter  to  calculate  just  how  much  power  must  be 
exerted  to  overcome  that  resistance,  and  move  the 
vehicle  a  certain  speed. 

In  a  flying  machine  the  same  thing  is  true,  but 
while  these  problems  may  be  known  in  a  general 
way,  the  aviator  has  several  unknown  elements 
ever  present,  which  make  estimates  difficult  to 
solve. 

THE  PULL  OF  THE  PKOPELLEK. — Two  such  fac- 
tors are  ever  present.  The  first  is  the  propeller 
pull.  The  energy  of  a  motor,  when  put  into  a 
propeller,  gives  a  pull  of  less  than  eight  pounds 
for  every  horse  power  exerted. 

FOOT  POUNDS. — The  work  produced  by  a  motor 
is  calculated  in  Foot  Pounds.  If  550  pounds 
should  be  lifted,  or  pulled,  one  foot  in  one  second 
of  time,  it  would  be  equal  to  one  horse  power. 

But  here  we  have  a  case  where  one  horse  power 
pulls  only  eight  pounds,  a  distance  of  one  foot 
within  one  second  of  time,  and  we  have  utilized 
less  than  one  sixty-fifth  of  the  actual  energy  pro- 
duced. 

SMALL  AMOUNT  OF  POWER  AVAILABLE. — This  is 


POWER  AND  ITS  APPLICATION     133 

due  to  two  things :  First,  the  exceeding  lightness 
of  the  air,  and  its  great  elasticity;  and,  second, 
the  difficulty  of  making  a  surface  which,  when  it 
strikes  the  air,  will  get  a  sufficient  grip  to  effect 
a  proper  pull. 

Now  it  must  be  obvious,  that  where  only  such 
a  small  amount  of  energy  can  be  made  available, 
in  a  medium  as  elusive  as  air,  the  least  change,  or 
form,  of  the  propeller,  must  have  an  important 
bearing  in  the  general  results. 

HIGH  PBOPELLEB  SPEED  IMPOBTANT. — Further- 
more, all  things  considered,  high  speed  is  impor- 
tant in  the  rotation  of  the  propeller,  up  to  a  cer- 
tain point,  beyond  which  the  pull  decreases  in 
proportion  to  the  speed.  High  speed  makes  a 
vacuum  behind  the  blade  and  thus  decreases  the 
effective  pull  of  the  succeeding  blade. 

WIDTH  AND  PITCH  or  BLADES. — If  the  blade  is 
too  wide  the  speed  of  the  engine  is  cut  down  to  a 
point  where  it  cannot  exert  the  proper  energy;  if 
the  pitch  is  very  small  then  it  must  turn  further  to 
get  the  same  thrust,  so  that  the  relation  of  diame- 
ter, pitch  and  speed,  are  three  problems  far  from 
being  solved. 

It  may  be  a  question  whether  the  propeller  form, 
as  we  now  know  it,  is  anything  like  the  true  or 
ultimate  shape,  which  will  some  day  be  discov- 
ered. 


134  AEROPLANES 

EFFECT  OF  INCREASING  PEOPELLEE  PULL. — If  the 
present  pull  could  be  doubled  what  a  wonderful 
revolution  would  take  place  in  aerial  navigation, 
and  if  it  were  possible  to  get  only  a  quarter  of 
the  effective  pull  of  an  engine,  the  results  would 
be  so  stupendous  that  the  present  method  of  fly- 
ing would  seem  like  child's  play  in  comparison. 

It  is  in  this  very  matter, — the  application  of 
the  power,  that  the  bird,  and  other  flying  crea- 
tures so  far  excel  what  man  has  done.  Calcula- 
tions made  with  birds  as  samples,  show  that  many 
of  them  are  able  to  fly  with  such  a  small  amount 
of  power  that,  if  the  same  energy  should  be  ap- 
plied to  a  flying  machine,  it  would  scarcely  drive 
it  along  the  ground. 

DISPOSITION  OF  THE  PLANES. — The  second  factor 
is  the  disposition  or  arrangement  of  the  planes 
with  relation  to  the  weight.  Let  us  illustrate  this 
with  a  concrete  example : 

We  have  an  aeroplane  with  a  sustaining  sur- 
face of  300  square  feet  which  weighs  900  pounds, 
or  30  pounds  per  square  foot  of  surface. 

DlFFEEENT  SPEEDS  WITH  SAME  POWEE. — NoW,  We 

may  be  able  to  do  two  things  with  an  airship  under 
those  conditions.    It  may  be  propelled  through 
the  air  thirty  miles  an  hour,  or  sixty  miles,  with 
the  expenditure  of  the  same  power. 
An  automobile,  if  propelled  at  sixty,  instead  of 


POWER  AND  ITS  APPLICATION     135 

thirty  miles  an  hour,  would  require  an  additional 
power  in  doing  so,  but  an  airship  acts  differently, 
within  certain  limitations. 

When  it  is  first  set  in  motion  its  effective  pull 
may  not  be  equal  to  four  pounds  for  each  horse 
power,  due  to  the  slow  speed  of  the  propeller,  and 
also  owing  to  the  great  angle  of  incidence  which 
resists  the  forward  movement  of  the  ship. 

INCEEASE  OF  SPEED  ADDS  TO  RESISTANCE. — Fi- 
nally, as  speed  increases,  the  angle  of  the  planes 
decrease,  resistance  is  less,  and  up  to  a  certain 
point  the  pull  of  the  propeller  increases ;  but  be- 
yond that  the  vacuum  behind  the  blades  becomes 
so  great  as  to  bring  down  the  pull,  and  there  is 
thus  a  balance, — a  sort  of  mutual  governing  mo- 
tion which,  together,  determine  the  ultimate  speed 
of  the  aeroplane. 

How  POWEE  DECEEASES  WITH  SPEED. — If  now, 
with  the  same  propeller,  the  speed  should  be 
doubled,  the  ship  would  go  no  faster,  because  the 
bite  of  the  propeller  on  the  air  would  be  ineffec- 
tive, hence  it  will  be  seen  that  it  is  not  the  amount 
of  power  in  itself,  that  determines  the  speed,  but 
the  shape  of  the  propeller,  which  must  be  so  made 
that  it  will  be  most  effective  at  the  speed  required 
for  the  ship. 

While  that  is  true  when  speed  is  the  matter  of 
greatest  importance,  it  is  not  the  case  where  it  is 


136  AEROPLANES 

desired  to  effect  a  launching.  In  that  case  the 
propeller  must,  be  made  so  that  its  greatest  pull 
will  be  at  a  slow  speed.  This  means  a  wider 
blade,  and  a  greater  pitch,  and  a  comparatively 
greater  pull  at  a  slow  speed. 

No  such  consideration  need  be  given  to  an  au- 
tomobile. The  constant  accretion  of  power  adds 
to  its  speed.  In  flying  machines  the  aviator  must 
always  consider  some  companion  factor  which 
must  be  consulted. 

How  TO  CALCULATE  THE  POWER  APPLIED. — In  a 
previous  chapter  reference  was  made  to  a  plane 
at  an  angle  of  forty-five  degrees,  to  which  two 
scales  were  attached,  one  to  get  its  horizontal  pull, 
or  drift,  and  the  other  its  vertical  pull,  or  lift. 

PULLING  AGAINST  AN  ANGLE. — Let  us  take  the 
same  example  in  our  aeroplane.  Assuming  that 
it  weighs  900  pounds,  and  that  the  angle  of  the 
planes  is  forty-five  degrees.  If  we  suppose  that 
the  air  beneath  the  plane  is  a  solid,  and  friction- 
less,  and  a  pair  of  scales  should  draw  it  up  the  in- 
cline, the  pull  in  doing  so  would  be  one-half  of  its 
weight,  or  450  pounds. 

It  must  be  obvious,  therefore,  that  its  force,  in 
moving  downwardly,  along  the  surface  A,  Fig.  60, 
would  be  450  pounds. 

The  incline  thus  shown  has  thereon  a  weight  B, 
mounted  on  wheels  C,  and  the  forwardly-project- 


POWER  AND  ITS  APPLICATION     137 

ing  cord  represents  the  power,  or  propeller  pull, 
which  must,  therefore,  exert  a  force  of  450  pounds 
to  keep  it  in  a  stationary  position  against  the  sur- 
face A. 

In  such  a  case  the  thrust  along  the  diagonal 
line  E  would  be  900  pounds,  being  the  composi- 
tion of  the  two  forces  pulling  along  the  lines  D,  F. 

THE  HORIZONTAL,  AND  VERTICAL  PULL. — Now  it 
must  be  obvious,  that  if  the  incline  takes  half  of 


v 
2^1 'ff.  €O.  Jforizoxfat  a/id  farttcal  pull. 

the  weight  while  it  is  being  drawn  forwardly,  in 
the  line  of  D,  if  we  had  a  propeller  drawing  along 
that  line,  which  has  a  pull  of  450  pounds,  it  would 
maintain  the  plane  in  flight,  or,  at  any  rate  hold 
it  in  space,,  assuming  that  the  air  should  be  mov- 
ing past  the  plane. 

The  table  of  lift  and  drift  gives  a  fairly  accurate 
method  of  determining  this  factor,  and  we  refer  to 
the  chapter  on  that  subject  which  will  show  the 
manner  of  making  the  calculations. 


138  AEEOPLANES 

THE  POWER  MOUNTING. — More  time  and  labor 
has  been  wasted,  in  airship  experiments,  in  poor 
motor  mounting,  than  in  any  other  direction. 
This  is  especially  true  where  two  propellers  are 
used,  or  where  the  construction  is  such  that  the 
propeller  is  mounted  some  distance  from  the  mo- 
tor. 

SECURING  THE  PROPELLER  TO  THE  SHAFT. — But 
even  where  the  propeller  is  mounted  on  the  en- 
gine shaft,  too  little  care  is  exercised  to  fix  it  se- 
curely. The  vibratory  character  of  the  mounting 
makes  this  a  matter  of  first  importance.  If  there 
is  a  solid  base  a  poorly  fixed  propeller  will  hold 
much  longer,  but  it  is  the  extreme  vibration  that 
causes  the  propeller  fastening  to  give  way. 

VIBRATIONS. — If  experimenters  realized  that  an 
insecure,  shaking,  or  weaving  bed  would  cause  a 
loss  of  from  ten  to  fifteen  per  cent,  in  the  pull  of 
the  propeller,  more  care  and  attention  would  be 
given  to  this  part  of  the  structure. 

WEAKNESSES  IN  MOUNTING. — The  general  weak- 
nesses to  which  attention  should  be  directed  are, 
first,  the  insecure  attachment  of  the  propeller  to 
the  shaft;  second,  the  liability  of  the  base  to 
weave ;  or  permit  of  a  torsional  movement ;  third, 
improper  bracing  of  the  base  to  the  main  body  of 
the  aeroplane. 

If  the  power  is  transferred  from  the  cylinder 


POWER  AND  ITS  APPLICATION     139 

to  the  engine  shaft  where  it  could  deliver  its  out- 
put without  the  use  of  a  propeller,  it  would  not 
be  so  important  to  consider  the  matter  of  vibra- 
tion; but  the  propeller,  if  permitted  to  vibrate, 
or  dance  about,  absorbs  a  vast  amount  of  energy, 
while  at  the  same  time  cutting  down  its  effective 
pull. 

Aside  from  this  it  is  dangerous  to  permit  the 
slightest  displacement  while  the  engine  is  run- 
ning. Any  looseness  is  sure  to  grow  worse,  in- 
stead of  better,  and  many  accidents  have  been 
registered  by  bolts  which  have  come  loose  from 
excessive  vibration.  It  is  well,  therefore,  to  have 
each  individual  nut  secured,  or  properly  locked, 
which  is  a  matter  easily  done,  and  when  so  secured 
there  is  but  little  trouble  in  going  over  the  ma- 
chine to  notice  just  how  much  more  the  nut  must 
be  taken  up  to  again  make  it  secure. 

THE  GASOLINE  TANK. — What  horrid  details  have 
been  told  of  the  pilots  who  have  been  burned  to 
death  with  the  escaping  gasoline  after  an  acci- 
dent, before  help  arrived.  There  is  no  excuse  for 
such  dangers.  Most  of  such  accidents  were  due 
to  the  old  practice  of  making  the  tanks  of  ex- 
ceedingly light  or  thin  material,  so  that  the  least 
undue  jar  would  tear  a  hole  at  the  fastening 
points,  and  thus  permit  the  gasoline  to  escape. 

A  thick  copper  tank  is  by  far  the  safest,  as  this 


140  AEROPLANES 

metal  will  not  readily  rupture  by  the  wrench  which 
is  likely  in  landing. 

WHERE  TO  LOCATE  THE  TANK. — There  has  been 
considerable  discussion  as  to  the  proper  place  to 
locate  the  tank.  Those  who  advocate  its  place- 
ment overhead  argue  that  in  case  of  an  accident 
the  aeroplane  is  likely  to  overturn,  and  the  tank 
will,  therefore,  be  below  the  pilot.  Those  who 
believe  it  should  be  placed  below,  claim  that  in 
case  of  overturning  it  is  safer  to  have  the  tank 
afire  above  than  below. 

DANGER  TO  THE  PILOT. — The  great  danger  to  the 
pilot,  in  all  cases  of  accidents,  lies  in  the  over- 
turning of  the  machine.  Many  have  had  accidents 
where  the  machine  landed  right  side  up,  even 
where  the  fall  was  from  a  great  height,  and  the 
only  damage  to  the  aviator  was  bruises.  Few,  if 
any,  pilots  have  escaped  where  the  machine  has 
overturned. 

It  is  far  better,  in  case  the  tank  is  light,  to  have 
it  detached  from  its  position,  when  the  ship  strikes 
the  earth,  because  in  doing  so,  it  will  not  be  so 
likely  to  burn  the  imprisoned  aviator. 

In  all  cases  the  tank  should  be  kept  as  far  away 
from  the  engine  as  possible.  There  is  no  reason 
why  it  cannot  be  placed  toward  the  tail  end  of 
the  machine,  a  place  of  safety  for  two  reasons: 
First,  it  is  out  of  the  reach  of  any  possible  dan- 


POWER  AND  ITS  APPLICATION     141 

ger  from  fire;  and,  second,  the  accidents  in  the 
past  show  that  the  tail  frame  is  the  least  likely  to 
be  injured. 

In  looking  over  the  illustrations  taken  from  the 
accidents,  notice  how  few  of  the  tails  are  even 
disarranged,  and  in  many  of  them,  while  the  en- 
tire fore  body  and  planes  were  crushed  to  atoms, 
the  tail  still  remained  as  a  relic,  to  show  its  com- 
parative freedom  from  the  accident. 

In  all  monoplanes  the  tail  really  forms  part  of 
the  supporting  surface  of  the  machine,  and  the 
adding  of  the  weight  of  the  gasoline  would  be 
placing  but  little  additional  duty  on  the  tail,  and 
it  could  be  readily  provided  for  by  a  larger  tail 
surface,  if  required. 

THE  CLOSED-IN  BODY. — The  closed-in  body  is  a 
vast  improvement,  which  has  had  the  effect  of 
giving  greater  security  to  the  pilot,  but  even  this 
is  useless  in  case  of  overturning. 

STARTING  THE  MACHINE. — The  direction  in  which 
improvements  have  been  slow  is  in  the  starting 
of  the  machine.  The  power  is  usually  so  mounted 
that  the  pilot  has  no  control  over  the  starting, 
as  he  is  not  in  a  position  to  crank  it. 

The  propeller  being  mounted  directly  on  the 
shaft,  without  the  intervention  of  a  clutch,  makes 
it  necessary,  while  on  the  ground,  for  the  pro- 
peller to  be  started  by  some  one  outside,  while 


142  AEROPLANES 

others  hold  the  machine  until  it  attains  the  proper 
speed. 

This  could  be  readily  remedied  by  using  a 
clutch,  but  in  the  past  this  has  been  regarded  as 
one  of  the  weight  luxuries  that  all  have  been  try- 
ing to  avoid.  Self  starters  are  readily  provided, 
and  this  with  the  provision  that  the  propeller  can 
be  thrown  in  or  out  at  will,  would  be  a  vast  im- 
provement in  all  machines. 

PEOPELLERS  WITH  VARYING  PITCH. — It  is  grow- 
ing more  apparent  each  day,  that  a  new  type  of 
propeller  must  be  devised  which  will  enable  the 
pilot  to  change  the  pitch,  as  the  speed  increases, 
and  to  give  a  greater  pitch,  when  alighting,  so 
as  to  make  the  power  output  conform  to  the  con- 
ditions. 

Such  propellers,  while  they  may  be  dangerous, 
and  much  heavier  than  the  rigid  type,  will,  no 
doubt,  appear  in  time,  and  the  real  improvement 
would  be  in  the  direction  of  having  the  blades 
capable  of  automatic  adjustment,  dependent  on 
the  wind  pressure,  or  the  turning  speed,  and  thus 
not  impose  this  additional  duty  on  the  pilot. 


CHAPTER  XI 

FLYING   MACHINE   ACCESSORIES 

THE  ANEMOMETER. — It  requires  an  expert  to 
judge  the  force  or  the  speed  of  a  wind,  and  even 
they  will  go  astray  in  their  calculations.  It  is 
an  easy  matter  to  make  a  little  apparatus  which 
will  accurately  indicate  the  speed.  A  device  of 
this  kind  is  called  an  Anemometer. 

Two  other  instruments  have  grown  out  of  this, 
one  to  indicate  the  pressure,  and  the  other  the 
direction  of  the  moving  air  current. 

THE  ANEMOGRAPH. — While  these  instruments  in- 
dicate, they  are  also  made  so  they  will  record  the 
speed,  the  pressure  and  the  direction,  and  the  de- 
vice for  recording  the  speed  and  pressure  is  called 
a  Anemograph. 

All  these  instruments  may  be  attached  to  the 
same  case,  and  thus  make  a  handy  little  device, 
which  will  give  all  the  information  at  a  glance. 

THE  ANEMOMETROGRAPH. — This  device  for  re- 
cording, as  well  as  indicating  the  speed,  pressure 
and  direction,  is  called  an  Anemometro graph. 
The  two  important  parts  of  the  combined  appa- 

143 


144  AEROPLANES 

ratus,  for  the  speed  and  pressure,  are  illustrated, 
to  show  the  principle  involved.  While  the  speed 
will  give  the  pressure,  it  is  necessary  to  make  a 
calculation  to  get  the  result  while  the  machine  does 
this  for  you. 


UJ.  61.    4peed  Itidicator. 

THE    SPEED    INDICATOR. — Four    hemispherical 
cups  A  are  mounted  on  four  radiating  arms  B, 


FLYING  MACHINE  ACCESSORIES     145 

which  are  secured  to  a  vertical  stem  C,  and 
adapted  to  rotate  in  suitable  bearings  in  a 
case,  which,  for  convenience  in  explaining,  is  not 
shown. 

On  the  lower  end  of  the  stem  C,  is  a  small  bevel 
pinion,  which  meshes  with  a  smaller  bevel  pinion 
within  the  base.  This  latter  is  on  a  shaft  which 
carries  a  small  gear  on  its  other  end,  to  mesh 


with  a  larger  gear  on  a  shaft  which  carries  a 
pointer  D  that  thus  turns  at  a  greatly  reduced 
speed,  so  that  it  can  be  easily  timed. 

AIR  PRESSURE  INDICATOR. — This  little  apparatus 
is  readily  made  of  a  base  A  which  is  provided 
with  two  uprights  B,  C,  through  the  upper  ends  of 
which  are  holes  to  receive  a  horizontally-disposed 
bar  D.  One  end  of  the  bar  is  a  flat  plane  sur- 


146  AEROPLANES 

face  E,  which  is  disposed  at  right  angles  to  the 
bar,  and  firmly  fixed  thereto. 

The  other  end  of  the  bar  has  a  lateral  pin  to 
serve  as  a  pivot  for  the  end  of  a  link  F,  its  other 
end  being  hinged  to  the  upper  end  of  a  lever  G, 
which  is  pivoted  to  the  post  C,  a  short  distance 
below  the  hinged  attachment  of  the  link  F,  so 
that  the  long  end  of  the  pointer  which  is  consti- 
tuted by  the  lever  G  is  below  its  pivot,  and  has, 
therefore,  a  long  range  of  movement. 

A  spring  I  between  the  upper  end  of  the  pointer 
G  and  the  other  post  B,  serves  to  hold  the  pointer 
at  a  zero  position.  A  graduated  scale  plate  J, 
within  range  of  the  pointer  will  show  at  a  glance 
the  pressure  in  pounds  of  the  moving  wind,  and 
for  this  purpose  it  would  be  convenient  to  make 
the  plane  E  exactly  one  foot  square. 

DETERMINING  THE  PRESSURE  FROM  THE  SPEED. — 
These  two  instruments  can  be  made  to  check  each 
other  and  thus  pretty  accurately  enable  you  to 
determine  the  proper  places  to  mark  the  pressure 
indicator,  as  well  as  to  make  the  wheels  in  the 
anemometer  the  proper  size  to  turn  the  pointer 
in  seconds  when  the  wind  is  blowing  at  a  certain 
speed,  say  ten  miles  per  hour. 

Suppose  the  air  pressure  indicator  has  the  scale 
divided  into  quarter  pound  marks.  This  will 
make  it  accurate  enough  for  all  purposes. 


FLYING  MACHINE  ACCESSORIES     147 

CALCULATING  PRESSURES  FROM  SPEED. — The  fol- 
lowing table  will  give  the  pressures  from  5  to  100 
miles  per  hour : 


Velocity  of  wind  in 
miles  per  hour 

Pressure 
per  sq.  ft. 

Velocity  of  wind  in 
miles  per  hour 

Pressure 
per  sq.ft. 

5   

.     .112 

55  

.15.125 

10   

.     .500 

60  

.  18.000 

15 

1  125 

65 

21  125 

20 

2000 

70 

22  500 

25   

.   3.12.5 

75  

.28.125 

30   

.   4.500 

80  

.  32.000 

35   

40 

.   6.125 

8  000 

85   
90 

.36.125 
40500 

45   
50   

.10.125 
.12.5 

95   
100  

.45.125 
.50.000 

How  THE  FIGURES  ARE  DETERMINED. — The  fore- 
going figures  are  determined  in  the  following  man- 
ner :  As  an  example  let  us  assume  that  the  veloc- 
ity of  the  wind  is  forty-five  miles  per  hour.  If 
this  is  squared,  or  45  multiplied  by  45,  the  product 
is  2025.  In  many  calculations  the  mathematician 
employs  what  is  called  a  constant,  a  figure  that 
never  varies,  and  which  is  used  to  multiply  or 
divide  certain  factors. 

In  this  case  the  constant  is  5/1000,  or,  as  usually 
written,  .005.  This  is  the  same  as  one  two  hun- 
dredths  of  the  squared  figure.  That  would  make 
the  problem  as  follows : 


148  AEROPLANES 

45  X  45  =  2025  -5-  200  =  10.125 ;  or, 
45  X  45  =  2025  X  .005  =  10.125. 

Again,  twenty-five  miles  per  hour  would  be 
25  X  25  =  625 ;  and  this  multiplied  by  .005  equals 
2  pounds  pressure. 

CONVERTING  HOURS  INTO  MINUTES. — It  is  some- 
times confusing  to  think  of  miles  per  hour,  when 
you  wish  to  express  it  in  minutes  or  seconds.  A 
simple  rule,  which  is  not  absolutely  accurate,  but 
is  correct  within  a  few  feet,  in  order  to  express 
the  speed  in  feet  per  minute,  is  to  multiply  the 
figure  indicating  the  miles  per  hour,  by  8%. 

To  illustrate:  If  the  wind  is  moving  at  the 
rate  of  twenty  miles  an  hour,  it  will  travel  in  that 
time  105,600  feet  (5280  X  20).  As  there  are  sixty 
minutes  in  an  hour,  105,600  divided  by  60,  equals 
1760  feet  per  minute.  Instead  of  going  through 
all  this  process  of  calculating  the  speed  per  min- 
ute, remember  to  multiply  the  speed  in  miles  per 
hour  by  90,  which  will  give  1800  feet. 

This  is  a  little  more  then  two  per  cent,  above 
the  correct  figure.  Again ;  40  X  90  equals  3600. 
As  the  correct  figure  is  3520,  a  little  mental  cal- 
culation will  enable  you  to  correct  the  figures  so 
as  to  get  it  within  a  few  feet. 

CHANGING  SPEED  HOURS  TO  SECONDS. — As  one- 
sixtieth  of  the  speed  per  minute  will  represent  the 
rate  of  movement  per  second,  it  is  a  comparatively 


FLYING  MACHINE  ACCESSORIES     149 

easy  matter  to  convert  the  time  from  speed  in 
miles  per  hour  to  fraction  of  a  mile  traveled  in 
a  second,  by  merely  taking  one-half  of  the  speed 
in  miles,  and  adding  it,  which  will  very  nearly  ex- 
press the  true  number  of  feet. 

As  examples,  take  the  following:  If  the  wind 
is  traveling  20  miles  an  hour,  it  is  easy  to  take 
one-half  of  20,  which  is  10,  and  add  it  to  20,  mak- 
ing 30,  as  the  number  of  feet  per  second.  If  the 
wind  travels  50  miles  per  hour,  add  25,  making 
75,  as  the  speed  per  second. 

The  correct  speed  per  second  of  a  wind  travel- 
ing 20  miles  an  hour  is  a  little  over  29  feet.  At 
50  miles  per  hour,  the  correct  figure  is  73y3  feet, 
which  show  that  the  figures  under  this  rule  are 
within  about  one  per  cent,  of  being  correct. 

With  the  table  before  you  it  will  be  an  easy 
matter,  by  observing  the  air  pressure  indicator, 
to  determine  the  proper  speed,  for  the  anemome- 
ter. Suppose  it  shows  a  pressure  of  two  pounds, 
which  will  indicate  a  speed  of  twenty  miles  an 
hour.  You  have  thus  a  fixed  point  to  start  from. 

PEESSUKE  AS  THE  SQUAKE  OF  THE  SPEED. — Now 
it  must  not  be  assumed  that  if  the  pressure  at 
twenty  miles  an  hour  is  two  pounds,  that  forty 
miles  an  hour  it  is  four  pounds.  The  pressure 
is  as  the  square  of  the  speed.  This  may  be  ex- 
plained as  follows :  As  the  speed  of  the  wind  in- 


150  AEROPLANES 

creases,  it  lias  a  more  effective  push  against  an 
object  than  its  rate  of  speed  indicates,  and  this 
is  most  simply  expressed  by  saying  that  each  time 
the  speed  is  doubled  the  pressure  is  four  times 
greater. 

As  an  example  of  this,  let  us  take  a  speed  of  ten 
miles  an  hour,  which  means  a  pressure  of  one- 
half  pound.  Double  this  speed,  and  we  have  20 
miles.  Multiplying  one-half  pound  by  4,  the  re- 
sult is  2  pounds.  Again,  double  20,  which  means 
40  miles,  and  multiplying  2  by  4,  the  result  is  8. 
Doubling  forty  is  eighty  miles  an  hour,  and  again 
multiplying  8  by  4,  we  have  32  as  the  pounds  pres- 
sure at  a  speed  of  80  miles  an  hour. 

The  anemometer,  however,  is  constant  in  its 
speed.  If  the  pointer  should  turn  once  a  second 
at  10  miles  an  hour,  it  would  turn  twice  at  20  miles 
an  hour,  and  four  times  a  second  at  40  miles  an 
hour. 

GYROSCOPIC  BALANCE. — Some  advance  has  been 
made  in  the  use  of  the  gyroscope  for  the  purpose 
of  giving  lateral  stability  to  an  aeroplane.  While 
the  best  of  such  devices  is  at  best  a  makeshift, 
it  is  well  to  understand  the  principle  on  which  they 
operate,  and  to  get  an  understanding  how  they  are 
applied. 

THE  PRINCIPLE  INVOLVED. — The  only  thing 
known  about  the  gyroscope  is,  that  it  objects  to 


FLYING  MACHINE  ACCESSOKIES     151 

changing  the  plane  of  its  rotation.  This  state- 
ment must  be  taken  with  some  allowance,  how- 
ever, as,  when  left  free  to  move,  it  will  change  in 
one  direction. 

To  explain  this  without  being  too  technical,  ex- 
amine Fig.  63,  which  shows  a  gyroscopic  top,  one 
end  of  the  rim  A,  which  supports  the  rotating 
wheel  B,  having  a  projecting  finger  C,  that  is 


mounted  on  a  pin-point  on  the  upper  end  of  the 
pedestal  D. 

When  the  wheel  B  is  set  in  rotation  it  will  main- 
tain itself  so  that  its  axis  E  is  horizontal,  or  at 
any  other  angle  that  the  top  is  placed  in  when  the 
wheel  is  spun.  If  it  is  set  so  the  axis  is  hori- 
zontal the  wheel  B  will  rotate  on  a  vertical  plane, 
and  it  forcibly  objects  to  any  attempt  to  make  it 


152  AEROPLANES 

turn  except  in  the   direction   indicated  by  the 
curved  arrows  F. 

The  wheel  B  will  cause  the  axis  E  to  swing 
around  on  a  horizontal  plane,  and  this  turning 
movement  is  always  in  a  certain  direction  in  re- 
lation to  the  turn  of  the  wheel  B,  and  it  is  ob- 
vious, therefore,  that  to  make  a  gyroscope  that 
will  not  move,  or  swing  around  an  axis,  the  plac- 
ing of  two  such  wheels  side  by  side,  and  rotated 
in  opposite  directions,  will  maintain  them  in  a 
fixed  position;  this  can  also  be  accomplished  by 


.  c/Ipplicaiton  of  the  Gyroscope. 


so  mounting  the  two  that  one  rotates  on  a  plane 
at  right  angles  to  the  other. 

THE  APPLICATION  OF  THE  GYROSCOPE.  —  Without 
in  any  manner  showing  the  structural  details  of 
the  device,  in  its  application  to  a  flying  machine, 
except  in  so  far  as  it  may  be  necessary  to  ex- 
plain its  operation,  we  refer  to  Fig.  64,  which 
assumes  that  A  represents  the  frame  of  the  aero- 
plane, and  B  a  frame  for  holding  the  gyroscopic 
wheel  C,  the  latter  being  mounted  so  it  rotates  on 
a  horizontal  plane,  and  the  frame  B  being  hinged 


FLYING  MACHINE  ACCESSORIES     153 

fore  and  aft,  so  that  it  is  free  to  swing  to  the  right 
or  to  the  left. 

For  convenience  in  explaining  the  action,  the 
planes  E  are  placed  at  right  angles  to  their  reg- 
ular positions,  F  being  the  forward  margin  of  the 
plane,  and  G  the  rear  edge.  Wires  H  connect 
the  ends  of  the  frame  B  with  the  respective 
planes,  or  ailerons,  E,  and  aW  ther  wire  I  joins 
the  downwardly-projecting  arms  of  the  two 
ailerons,  so  that  motion  is  transmitted  to  both  at 


.  Action  of  the  Gyroscope. 


the  same  time,  and  by  a  positive  motion  in  either 
direction. 

In  the'  second  figure,  65,  the  frame  of  the  aero- 
plane is  shown  tilted  at  an  angle,  so  that  its  right 
side  is  elevated.  As  the  gyroscopic  wheel  remains 
level  it  causes  the  aileron  on  the  right  side  to 
change  to  a  negative  angle,  while  at  the  same 
time  giving  a  positive  angle  to  the  aileron  on  the 
left  side,  which  would,  as  a  result,  depress  the 
right  side,  and  bring  the  frame  of  the  machine 
back  to  a  horizontal  position. 

FOKE  AND  ATT  GYROSCOPIC  CONTROL. — It  is  ob- 


154  AEROPLANES 

vious  that  the  same  application  of  this  force  may 
be  applied  to  control  the  ship  fore  and  aft,  al- 
though it  is  doubtful  whether  such  a  plan  would 
have  any  advantages,  since  this  should  be  wholly 
within  the  control  of  the  pilot. 

Laterally  the  ship  should  not  be  out  of  balance ; 
fore  and  aft  this  is  a  necessity,  and  as  the  great 
trouble  with  all  aeroplanes  is  to  control  them 
laterally,  it  may  well  be  doubted  whether  it  would 
add  anything  of  value  to  the  machine  by  having 
an  automatic  fore  and  aft  control,  which  might, 
in  emergencies,  counteract  the  personal  control  of 
the  operator. 

ANGLE  INDICATOK. — In  flight  it  is  an  exceedingly 
difficult  matter  for  the  pilot  to  give  an  accurate 
idea  of  the  angle  of  the  planes.  If  the  air  is 
calm  and  he  is  moving  over  a  certain  course,  and 
knows,  from  experience,  what  his  speed  is,  he  may 
be  able  to  judge  of  this  factor,  but  he  cannot  tell 
what  changes  take  place  under  certain  conditions 
during  the  flight. 

For  this  purpose  a  simple  little  indicator  may 
be  provided,  shown  in  Fig.  66,  which  is  merely  a 
vertical  board  A,  with  a  pendulum  B,  swinging 
fore  and  aft  from  a  pin  C  which  projects  out 
from  the  board  a  short  distance  above  its  center. 

The  upper  end  of  the  pendulum  has  a  heart- 
shaped  wire  structure  D,  that  carries  a  sliding 


FLYING  MACHINE  ACCESSOEIES     155 

weight  E.  Normally,  when  the  aeroplane  is  on 
an  even  keel,  or  is  even  at  an  angle,  the  weight 
E  rests  within  the  bottom  of  the  loop  D,  but 
should  there  be  a  sudden  downward  lurch  or  a 
quick  upward  inclination,  which  would  cause  the 
pendulum  below  to  rapidly  swing  in  either  direc- 


tion,  the  sliding  weight  E  would  at  once  move 
forward  in  the  same  direction  that  the  pendulum 
had  moved,  and  thus  counteract,  for  the  instant 
only,  the  swing,  when  it  would  again  drop  back 
into  its  central  position. 

With  such  an  arrangement,  the  pendulum  would 
hang  vertically  at  all  times,  and  the  pointer  be- 
low, being  in  range  of  a  circle  with  degrees  in- 


156  AEROPLANES 

dicated  thereon,  and  the  base  attached  to  the 
frame  of  the  machine,  can  always  be  observed, 
and  the  conditions  noted  at  the  time  the  changes 
take  place. 

PENDULUM  STABILIZER. — In  many  respects  the 
use  of  a  pendulum  has  advantages  over  the  gyro- 
scope. The  latter  requires  power  to  keep  it  in 
motion.  The  pendulum  is  always  in  condition 
for  service.  While  it  may  be  more  difficult  to 
adjust  the  pendulum,  so  that  it  does  not  affect 


tiimte 


the  planes  by  too  rapid  a  swing,  or  an  oscillation 
which  is  beyond  the  true  angle  desired,  still,  these 
are  matters  which,  in  time,  will  make  the  pen- 
dulum a  strong  factor  in  lateral  stability. 

It  is  an  exceedingly  simple  matter  to  attach  the 
lead  wires  from  an  aileron  to  the  pendulum.  In 
Fig.  67  one  plan  is  illustrated.  The  pendulum 
A  swings  from  the  frame  B  of  the  machine,  the 
ailerons  C  being  in  this  case  also  shown  at  right 
angles  to  their  true  positions. 


FLYING  MACHINE  ACCESSOBIES     157 

The  other,  Fig.  68,  assumes  that  the  machine  is 
exactly  horizontal,  and  as  the  pendulum  is  in  a 
vertical  position,  the  forward  edges  of  both  aile- 
rons are  elevated,  but  when  the  pendulum  swings 
both  ailerons  will  be  swung  with  their  forward 
margins  up  or  down  in  unison,  and  thus  the  proper 
angles  are  made  to  right  the  machine. 

STEERING  AND  CONTROLLING  WHEEL. — For  the 
purpose  of  concentrating  the  control  in  a  single 
wheel,  which  has  not  alone  a  turning  motion,  but 


is  also  mounted  in  such  a  manner  that  it  will  oscil- 
late to  and  fro,  is  very  desirable,  and  is  adapted 
for  any  kind  of  machine. 

Fig.  69  shows  such  a  structure,  in  which  A 
represents  the  frame  of  the  machine,  and  B  a 
segment  for  the  stem  of  the  wheel,  the  segment 
being  made  of  two  parts,  so  as  to  form  a  guide- 
way  for  the  stem  C  to  travel  between,  and  the  seg- 
ment is  placed  so  that  the  stem  will  travel  in  a 
fore  and  aft  direction. 


158 


AEROPLANES 


The  lower  end  of  the  stem  is  mounted  in  a 
socket,  at  D,  so  that  while  it  may  be  turned,  it 
will  also  permit  this  oscillating  motion.  Near  its 
lower  end  is  a  cross  bar  E  from  which  the  wires 
run  to  the  vertical  control  plane,  and  also  to  the 
ailerons,  if  the  machine  is  equipped  with  them,  or 
to  the  warping  ends  of  the  planes. 


Above  the  cross  arms  is  a  loose  collar  F  to 
which  the  fore  and  aft  cords  are  attached  that  go 
to  the  elevators,  or  horizontal  planes.  The  upper 
end  of  the  stem  has  a  wheel  G,  which  may  also  be 
equipped  with  the  throttle  and  spark  levers. 

AUTOMATIC  STABILIZING  WINGS. — Unquestion- 
.ably,  the  best  stabilizer  is  one  which  will  act  on 
its  own  initiative.  The  difficulty  with  automatic 
devices  is,  that  they  act  too  late,  as  a  general 
thing,  to  be  effective.  The  device  represented  in 


FLYING  MACHINE  ACCESSOEIES     159 

Fig.  70  is  very  simple,  and  in  practice  is  found  to 
be  most  efficient. 

In  this  Fig.  70  A  and  B  represent  the  upper 
and  the  lower  planes,  respectively.     Near  the  end 


c 

' 

t 

f-JT                                                                                W 

vertical  standards  C,  D,  are  narrow  wings  E  E, 
F  F,  hinged  on  a  fore  and  aft  line  close  below 
each  of  the  planes,  the  wings  being  at  such  dis- 
tances from  the  standards  C  D  that  when  they 
swing  outwardly  they  will  touch  the  standards, 


and  when  in  that  position  will  be  at  an  angle  of 
about  35  degrees  from  the  planes  A  B. 

Inwardly  they  are  permitted  to  swing  up  and 
lie  parallel  with  the  planes,  as  shown  in  Fig.  71 


160  AEROPLANES 

where  the  planes  are  at  an  angle.  In  turning,  all 
machines  skid, — that  is  they  travel  obliquely 
across  the  field,  and  this  is  also  true  when  the 
ship  is  sailing  at  right  angles  to  the  course  of  the 
wind. 

This  will  be  made  clear  by  reference  to  Fig. 
72,  in  which  the  dart  A  represents  the  direction 
of  the  movement  of  the  aeroplane,  and  B  the  di- 


rection  of  the  wind,  the  vertical  rudder  C  being 
almost  at  right  angles  to  the  course  of  the  wind. 
In  turning  a  circle  the  same  thing  takes  place 
as  shown  in  Fig.  73,  with  the  tail  at  a  different 
angle,  so  as  to  give  a  turning  movement  to  the 
plane.  It  will  be  seen  that  in  the  circling  move- 
ment the  tendency  of  the  aeroplane  is  to  fly  out 
at  a  tangent,  shown  by  the  line  D,  so  that  the 
planes  of  the  machine  are  not  radially-disposed 


FLYING  MACHINE  ACCESSORIES     161 

with  reference  to  the  center  of  the  circle,  the  line 
E  showing  the  true  radial  line. 

Eeferring  now  to  Fig.  71,  it  will  be  seen  that 
this  skidding  motion  of  the  machine  swings  the 
wings  F  F  inwardly,  so  that  they  offer  no  resis- 
tance to  the  oblique  movement,  but  the  wings  E 
E,  at  the  other  end  of  the  planes  are  swung  out- 
wardly, to  provide  an  angle,  which  tends  to  raise 


up  the  inner  end  of  the  planes,  and  thereby  seek 
to  keep  the  planes  horizontal. 

BAROMETERS. — These  instruments  are  used  for 
registering  heights.  A  barometer  is  a  device  for 
measuring  the  weight  or  pressure  of  the  air. 
The  air  is  supposed  to  extend  to  a  height  of  40 
miles  from  the  surface  of  the  sea.  A  column  of 
air  one  inch  square,  and  forty  miles  high,  weighs 
the  same  as  a  column  of  mercury  one  inch  square 
and  30  inches  high. 


162 


AEROPLANES 


Such  a  column  of  air,  or  of  mercury,  weighs 
143/4  pounds.  If  the  air  column  should  be 
weighed  at  the  top  of  the  mountain,  that  part 
above  would  weigh  less  than  if  measured  at  the 
sea  level,  hence,  as  we  ascend  or  descend  the  pres- 
sure becomes  less  or  more,  dependent  on  the  al- 
titude. 

Mercury  is  also  used  to  indicate  temperature, 
but  this  is  brought  about  by  the  expansive  quality 
of  the  mercury,  and  not  by  its  weight. 


t/fncroid  Bwo/nefet. 


ANEROID  BAROMETEK. — The  term  Aneroid  ba- 
rometer is  frequently  used  in  connection  with  air- 
ship experiments.  The  word  aneroid  means  not 
wet,  or  not  a  fluid,  like  mercury,  so  that,  while 
aneroid  barometers  are  being  made  which  do  use 
mercury,  they  are  generally  made  without. 

One  such  form  is  illustrated  in  Fig.  74,  which 
represents  a  cylindrical  shell  A,  which  has  at  each 
end  a  head  of  concentrically  formed  corrugations. 
These  heads  are  securely  fixed  to  the  ends  of  the 
shell  A.  Within,  one  of  the  disk  heads  has  a 


FLYING  MACHINE  ACCESSORIES     163 

short  stem  C,  which  is  attached  to  the  short  end 
of  a  lever  D,  this  lever  being  pivoted  at  E.  The 
outer  end  of  this  lever  is  hinged  to  the  short  end 
of  another  lever  F,  and  so  by  compounding  the 
levers,  it  will  be  seen  that  a  very  slight  movement 
of  the  head  B  will  cause  a  considerable  movement 
in  the  long  end  of  the  lever  F. 

This  end  of  the  lever  F  connects  with  one  limb 
of  a  bell-crank  lever  G,  and  its  other  limb  has  a 
toothed  rack  connection  with  a  gear  H,  which 
turns  the  shaft  to  which  the  pointer  I  is  attached. 

Air  is  withdrawn  from  the  interior  of  the  shell, 
so  that  any  change  in  the  pressure,  or  weight  of 
the  atmosphere,  is  at  once  felt  by  the  disk  heads, 
and  the  finger  turns  to  indicate  the  amount  of 
pressure. 

HYDROPLANES. — Hydro  means  water,  hence  the 
term  hydroplane  has  been  given  to  machines 
which  have  suitable  pontoons  or  boats,  so  they 
may  alight  or  initiate  flight  from  water. 

There  is  no  particular  form  which  has  been 
adopted  to  attach  to  aeroplanes,  the  object  gen- 
erally being  to  so  make  them  that  they  will  sus- 
tain the  greatest  amount  of  weight  with  the  least 
submergence,  and  also  offer  the  least  resistance 
while  the  motor  is  drawing  the  machine  along  the 
surface  of  the  water,  preparatory  to  launching  it. 

SUSTAINING  WEIGHT  OP  PONTOONS. — A  pontoon 


164  -AEKOPLANES 

having  within  nothing  but  air,  is  merely  a  meas- 
uring device  which  determines  the  difference  be- 
tween the  weight  of  water  and  the  amount  placed 
on  the  pontoon.  "Water  weighs  62^  pounds  per 
cubic  foot.  Ordinary  wood,  an  average  of  32 
pounds,  and  steel  500  pounds. 

It  is,  therefore,  an  easy  matter  to  determine 
how  much  of  solid  matter  will  be  sustained  by  a 
pontoon  of  a  given  size,  or  what  the  dimensions 
of  a  pontoon  should  be  to  hold  up  an  aeroplane 
which  weighs,  with  the  pilot,  say,  1100  pounds. 

As  we  must  calculate  for  a  sufficient  excess  to 
prevent  the  pontoons  from  being  too  much  im- 
mersed, and  also  allow  a  sufficient  difference  in 
weight  so  that  they  will  keep  on  the  surface  when 
the  aeroplane  strikes  the  surface  in  alighting,  we 
will  take  the  figure  of  1500  pounds  to  make  the 
calculations  from. 

If  this  figure  is  divided  by  62y2  we  shall  find 
the  cubical  contents  of  the  pontoons,  not  consider- 
ing, of  course,  the  weight  of  the  material  of  which 
they  are  composed.  This  calculation  shows  that 
we  must  have  24  cubic  feet  in  the  pontoons. 

As  there  should  be  two  main  pontoons,  and  a 
smaller  one  for  the  rear,  each  of  the  main  ones 
might  have  ten  cubic  feet,  and  the  smaller  one 
four  cubic  feet. 

SHAPES  OF  THE  PONTOONS. — We  are  now  ready 


FLYING  MACHINE  ACCESSORIES     165 

to  design  the  shapes.  Fig.  75  shows  three  gen- 
eral types,  A  being  made  rectangular  in  form, 
with  a  tapering  forward  end,  so  constructed  as  to 
ride  up  on  the  water. 

The  type  B  has  a  rounded  under  body,  the  for- 
ward end  being  also  skiff-shaped  to  decrease  as 
much  as  possible  the  resistance  of  the  water  im- 
pact. 


The  third  type  C  is  made  in  the  form  of  a 
closed  boat,  with  both  ends  pointed,  and  the  bot- 
tom rounded,  or  provided  with  a  keel.  Or,  as  in 
some  cases  the  body  may  be  made  triangular  in 
cross  section  so  that  as  it  is  submerged  its  sus- 
taining weight  will  increase  at  a  greater  degree 
as  it  is  pressed  down  than  its  vertical  measure- 
ment indicates. 


166  AEROPLANES 

All  this,  however,  is  a  matter  left  to  the  judg- 
ment of  the  designer,  and  is,  in  a  great  degree, 
dependent  on  the  character  of  the  craft  to  which 
it  is  to  be  applied. 


CHAPTER  XII 

EXPERIMENTAL  WOKK  IN  FLYING 

THE  novice  about  to  take  his  first  trial  trip  in 
an  automobile  will  soon  learn  that  the  great  task 
in  his  mind  is  to  properly  start  the  machine.  He 
is  conscious  of  one  thing,  that  it  will  be  an  easy 
matter  to  stop  it  by  cutting  off  the  fuel  supply 
and  applying  the  brakes. 

CERTAIN  CONDITIONS  IN  FLYING. — In  an  aero- 
plane conditions  are  reversed.  Shutting  off  the 
fuel  supply  and  applying  the  brakes  only  bring 
on  the  main  difficulty.  He  must  learn  to  stop  the 
machine  after  all  this  is  done,  and  this  is  the 
great  test  of  flying.  It  is  not  the  launching, — 
the  ability  to  get  into  the  air,  but  the  landing,  that 
gives  the  pupil  his  first  shock. 

Man  is  so  accustomed  to  the  little  swirls  of  air 
all  about  him,  that  he  does  not  appreciate  \rhat 
they  mean  to  a  machine  which  is  once  free  to 
glide  along  in  the  little  currents  which  are  so  un- 
noticeable  to  him  as  a  pedestrian. 

The  contour  of  the  earth,  the  fences,  trees,  lit- 
tle elevations  and  other  natural  surroundings,  all 

167 


168  AEROPLANES 

have  their  effect  on  a  slight  moving  air  current, 
and  these  inequalities  affect  the  air  and  disturb 
it  to  a  still  greater  extent  as  the  wind  increases. 
Even  in  a  still  air,  with  the  sun  shining,  there  are 
air  eddies,  caused  by  the  uneven  heating  of  the 
air  in  space. 

HEAT  IN  AIR. — Heat  is  transmitted  through  the 
air  by  what  is  called  convection,  that  is,  the  par- 
ticles of  the  air  transmit  it  from  one  point  to  the 
next.  If  a  room  is  closed  up  tight,  and  a  little 
aperture  provided  so  as  to  let  in  a  streak  of  sun- 
light, it  will  give  some  idea  of  the  unrest  of  the 
atmosphere.  This  may  be  exhibited  by  smoke 
along  the  line  of  the  sun's  rays,  which  indicates 
that  the  particles  of  air  are  constantly  in  motion, 
although  there  may  be  absolutely  nothing  in  the 
room  to  disturb  it. 

MOTION  WHEN  IN  FLIGHT. — If  you  can  imagine 
a  small  airship  floating  in  that  space,  you  can 
readily  conceive  that  it  will  be  hurled  hither  and 
thither  by  the  motion  which  is  thus  apparent  to 
the  eye. 

This  motion  is  greatly  accentuated  by  the  sur- 
face of  the  earth,  independently  of  its  uneven  con- 
tour. If  a  ball  is  thrown  through  the  air,  its 
dynamic  force  is  measured  by  its  impact.  So 
with  light,  and  heat.  In  the  space  between  the 
planets  it  is  very  cold.  The  sunlight,  or  the  rays 


EXPERIMENTAL  WORK  IN  FLYING     169 

from  the  sun  are  there,  just  the  same  as  on  the 
earth. 

Unless  the  rays  come  into  contact  with  some- 
thing, they  produce  no  effect.  When  the  beams 
from  the  sun  come  into  contact  with  the  atmos- 
phere a  dynamic  force  is  exerted,  just  the  same 
as  when  the  ball  struck  an  object.  When  the  rays 
reach  the  earth,  reflection  takes  place,  and  these 
reflected  beams  act  on  the  air  under  different  con- 
ditions. 

CHANGING  ATMOSPHERE. — If  the  air  is  full  of 
moisture,  as  it  may  be  at  some  places,  while  com- 
paratively dry  at  other  points,  the  reflection 
throughout  the  moist  area  is  much  greater  than  in 
the  dry  places,  hence  evaporation  will  take  place 
and  whenever  a  liquid  vaporizes  it  means  heat. 

On  the  other  hand,  when  the  vapor  is  turning 
to  a  liquid,  condensation  takes  place,  and  that 
means  cooling.  If  the  air  should  be  of  the  same 
degree  of  saturation  throughout, — that  is,  have 
the  same  amount  of  moisture  everywhere,  there 
would  be  few  winds.  These  remarks  apply  to 
conditions  which  exist  over  low  altitudes  all  over 
the  earth. 

But  at  high  altitudes  the  conditions  are  entirely 
different.  As  we  ascend  the  air  becomes  rarer. 
It  has  less  moisture,  because  a  wet  atmosphere, 
being  heavier,  lies  nearer  the  surface  of  the  earth. 


170  AEROPLANES 

Being  rarer  the  action  of  sunlight  on  the  particles 
is  less  intense.  Reflection  and  refraction  of  the 
rays  acting  on  the  light  atmosphere  do  not  pro- 
duce such  a  powerful  effect  as  on  the  air  near  the 
ground. 

All  these  conditions — the  contour  of  the  earth; 
the  uneven  character  of  the  moisture  in  the  air; 
the  inequalities  of  the  convection  currents;  and 
the  unstable,  tenuous,  elastic  nature  of  the  atmos- 
phere, make  the  trials  of  the  aviator  a  hazardous 
one,  and  it  has  brought  out  numerous  theories 
connected  with  bird  flight.  One  of  these  assumes 
that  the  bird,  by  means  of  its  finely  organized 
sense,  is  able  to  detect  rising  air  currents,  and  it 
selects  them  in  its  flight,  and  by  that  means  is  en- 
abled to  continue  in  flight  indefinitely,  by  soaring, 
or  by  flapping  its  wings. 

ASCENDING  CURRENTS. — It  has  not  been  explained 
how  it  happens  that  these  particular  "  ascending 
currents"  always  appear  directly  in  the  line  of 
the  bird  flight ;  or  why  it  is  that  when,  for  instance, 
a  flock  of  wild  geese  which  always  fly  through 
space  in  an  A-shaped  formation,  are  able  to  get 
ascending  air  currents  over  the  wide  scope  of  space 
they  cover. 

ASPIRATE  CURRENTS. — Some  years  ago,  in  mak- 
ing experiments  with  the  outstretched  wings  of 
one  of  the  large  soaring  birds,  a  French  sailor 


EXPERIMENTAL  WORK  IN  FLYING     171 

was  surprised  to  experience  a  peculiar  pulling  mo- 
tion, when  the  bird's  wings  were  held  at  a  certain 
angle,  so  that  the  air  actually  seemed  to  draw  it 
into  the  teeth  of  the  current. 

It  is  known  that  if  a  ball  is  suspended  by  a 
string,  and  a  jet  of  air  is  directed  against  it,  in 
a  particular  way,  the  ball  will  move  toward  the 
jet,  instead  of  being  driven  away  from  it.  A  well 
known  spraying  device,  called  the  "ball  nozzle," 
is  simply  a  ball  on  the  end  of  a  nozzle,  and  the 
stream  of  water  issuing  is  not  effectual  to  drive 
the  ball  away. 

From  the  bird  incident  alluded  to,  a  new  theory 
was  propounded,  namely,  that  birds  flew  because 
of  the  aspirated  action  of  the  air,  and  the  wings 
and  body  were  so  made  as  to  cause  the  moving  air 
current  to  act  on  it,  and  draw  it  f  orwardly. 

OUTSTEETCHED  WINGS. — This  only  added  to  the 
"bird  wing"  theory  a  new  argument  that  all  fly- 
ing things  must  have  outstretched  wings,  in  order 
to  fly,  forgetting  that  the  ball,  which  has  no-  out- 
stretched wings,  has  also  the  same  "aspirate" 
movement  attributed  to  the  wings  of  the  bird. 

The  foregoing  remarks  are  made  in  order  to  im- 
press on  the  novice  that  theories  do  not  make 
flying  machines,  and  that  speculations,  or  analo- 
gies of  what  we  see  all  about  us,  will  not  make  an 
aviator.  A  flying  machine  is  a  question  of  dy- 


172  AEROPLANES 

namics,  just  as  surely  as  the  action  of  the  sun  on 
the  air,  and  the  movements  of  the  currents,  and 
the  knowledge  of  applying  those  forces  in  the  fly- 
ing machine  makes  the  aviator. 

THE  STAETING  POINT. — Before  the  uninitiated 
should  attempt  to  even  mount  a  machine  he  should 
know  what  it  is  composed  of,  and  how  it  is  made. 
His  investigation  should  take  in  every  part  of  the 
mechanism ;  he  should  understand  about  the  plane 
surface,  what  the  stresses  are  upon  its  surface, 
what  is  the  duty  of  each  strut,  or  brace  or  wire 
and  be  able  to  make  the  proper  repairs. 

THE  VITAL  PAKT  OF  THE  MACHINE. — The  motor, 
the  life  of  the  machine  itself,  should  be  like  a 
book  to  him.  It  is  not  required  that  he  should 
know  all  the  theories  which  is  necessary  in  the 
building,  as  to  the  many  features  which  go  to 
make  up  a  scientifically-designed  motor;  but  he 
must  know  how  and  why  it  works.  He  should  un- 
derstand the  cam  action,  whereby  the  valves  are 
lifted  at  the  proper  time;  what  the  effect  of  the 
spark  advance  means;  the  throttling  of  the  en- 
gine; air  admission  and  supply;  the  regulation 
of  the  carbureter;  its  mechanism  and  construc- 
tion; the  propeller  should  be  studied,  and  its  ac- 
tion at  various  speeds. 

STUDYING  THE  ACTION  OF  THE  MACHINE. — Then 
comes  the  study  on  the  seat  of  the  machine  itself. 


EXPEEIMENTAL  WORK  IN  FLYING     173 

It  will  be  a  novel  sensation.  Before  him  is  the 
steering  wheel,  if  it  should  be  so  equipped.  Turn- 
ing it  to  the  right,  swings  the  vertical  tail  plane 
so  the  machine  will  turn  to  the  right.  Certainly, 
he  knows  that;  but  how  far  must  he  turn  the 
wheel  to  give  it  a  certain  angle. 

It  is  not  enough  to  know  that  a  lever  or  a  wheel 
when  moved  a  certain  way  will  move  a  plane  a 
definite  direction.  He  should  learn  to  know  in- 
stinctively, how  far  a  movement  to  make  to  get 
a  certain  result  in  the  plane  itself,  and  under  run- 
ning conditions,  as  well. 

Suppose  we  have  an  automobile,  running  at  the 
rate  of  ten  miles  an  hour,  and  the  chauffeur  turns 
the  steering  wheel  ten  degrees.  He  can  do  so  with 
perfect  safety ;  but  let  the  machine  be  going  forty 
miles  an  hour,  and  turn  the  wheel  ten  degrees, 
and  it  may  mean  an  accident.  In  one  case  the 
machine  is  moving  144/2  feet  a  second,  and  in  the 
other  instance  58  feet. 

If  the  airship  has  a  lever  for  controlling  the 
angle  of  flight,  he  must  study  its  arrangement, 
and  note  how  far  it  must  be  moved  to  assume 
the  proper  elevating  angle.  Then  come  the  means 
for  controlling  the  lateral  stability  of  the  machine. 
All  these  features  should  be  considered  and  studied 
over  and  over,  until  you  have  made  them  your 
friends. 


174  AEROPLANES 

While  thus  engaged,  you  are  perfectly  sure  that 
you  can  remember  and  act  on  a  set  of  complicated 
movements.  You  imagine  that  you  are  skimming 
over  the  ground,  and  your  sense  tells  you  that  you 
have  sufficient  speed  to  effect  a  launching.  In 
your  mind  the  critical  time  has  come. 

ELEVATING  THE  MACHINE. — Simply  give  the  ele- 
vator lever  the  proper  angle,  sharp  and  quick  and 
up  you  go.  As  the  machine  responds,  and  you  can 
feel  the  cushioning  motion,  which  follows,  as  it  be- 
gins to  ride  the  air,  you  are  aware  of  a  sensation 
as  though  the  machine  were  about  to  turn  over 
to  one  side;  you  think  of  the  lateral  control  at 
once,  but  in  doing  so  forget  that  the  elevator  must 
be  changed,  or  you  will  go  too  high. 

You  forget  about  the  earth ;  you  are  too  busy 
thinking  about  several  things  which  seem  to  need 
your  attention.  Yes,  there  are  a  variety  of  mat- 
ters which  will  crowd  upon  you,  each  of  which  re- 
quire two  things ;  the  first  being  to  get  the  proper 
lever,  and  the  second,  to  move  it  just  so  far. 

In  the  early  days  of  aeroplaning,  when  accidents 
came  thick  and  fast,  the  most  usual  explanation 
which  came  from  the  pilot,  when  he  recovered, 
was:  "I  pushed  the  lever  too  far." 

Hundreds  of  trial  machines  were  built,  when 
man  learned  that  he  could  fly,  and  in  every  in- 
stance, it  is  safe  to  say,  the  experimenter  made  the 


EXPERIMENTAL  WORK  IN  FLYING     175 

most  strenuous  exertion  to  get  up  in  the  air  the 
first  time  the  machine  was  put  on  the  trial  ground. 

It  is  a  wonder  that  accidents  were  not  recorded 
by  the  hundreds,  instead  of  by  the  comparatively 
few  that  were  heard  from.  It  was  very  discour- 
aging, no  doubt,  that  the  machines  would  not  fly, 
but  that  all  of  them,  if  they  had  sufficient  power, 
would  fly,  there  can  be  no  doubt. 

How  TO  PRACTICE. — Absolute  familiarity  with 
every  part  of  the  machine  and  conditions  is  the 
first  thing.  The  machine  is  brought  out,  and  the 
engine  tested,  the  machine  being  held  in  leash 
while  this  is  done.  It  is  then  throttled  down  so 
that  the  power  of  the  engine  will  be  less  than  is 
necessary  to  raise  the  machine  from  the  ground. 

THE  FIRST  STAGE. — Usually  it  will  require  over 
25  miles  an  hour  to  raise  the  machine.  The  engine 
is  set  in  motion,  and  now,  for  the  first  time  a  new 
sensation  takes  possession  of  you,  for  the  reason 
that  you  are  cut  off  from  communication  with 
those  around  you  as  absolutely  as  though  they 
were  a  hundred  miles  away. 

This  new  dependence  on  yourself  is,  in  itself, 
one  of  the  best  teachers  you  could  have,  because 
it  begins  to  instill  confidence  and  control.  As  the 
machine  darts  forward,  going  ten  or  fifteen  miles 
an  hour,  with  the  din  of  the  engine  behind  you, 
and  feeling  the  rumbling  motion  of  the  wheels 


176  AEROPLANES 

over  the  uneven  surface  of  the  earth,  you  have  the 
sensation  of  going  forty  miles  an  hour. 

The  newness  of  the  first  sensation,  which  is 
always  under  those  conditions  very  much  aug- 
mented in  the  mind,  wears  away  as  the  machine 
goes  back  and  forth.  There  is  only  one  control 
that  requires  your  care,  namely,  to  keep  it  on  a 
straight  course.  This  is  easy  work,  but  you  are 
learning  to  make  your  control  a  reflex  action, — to 
do  it  without  exercising  a  distinct  will  power. 

PATIENCE  THE  MOST  DIFFICULT  THING. — If  you 
have  the  patience,  as  you  should,  to  continue  this 
running  practice,  until  you  absolutely  eliminate 
the  right  and  left  control,  as  a  matter  of  thought, 
occasionally,  if  the  air  is  still  turning  the  ma- 
chine, and  eventually,  bringing  it  back,  by  turning 
it  completely  around,  while  skimming  the  ground, 
you  will  be  ready  for  the  second  stage  in  the 
trials. 

THE  SECOND  STAGE. — The  engine  is  now  ar- 
ranged so  that  it  will  barely  lift,  when  running 
at  its  best.  After  the  engine  is  at  full  speed,  and 
you  are  sure  the  machine  is  going  fast  enough, 
the  elevator  control  is  turned  to  point  the  machine 
in  the  air.  It  is  a  tense  moment.  You  are  on  the 
alert. 

The  elevator  is  turned,  and  the  forward  end 
changes  its  relation  with  the  ground  before  you. 


EXPERIMENTAL  WORK  IN  FLYING     177 

There  "was  a  slight  lift,  but  your  caution  induces 
you  to  return  the  planes  to  their  normal  running 
angle.  You  try  it  again.  You  are  now  certain 
that  the  machine  made  a  leap  and  left  the  ground. 
This  is  the  exhilarating  moment. 

With  a  calm  air  the  machine  is  turned  while 
running,  by  means  of  the  vertical  rudders.  This 
is  an  easy  matter,  because  while  going  at  twenty 
miles  an  hour,  the  weight  of  the  machine  on  the 
surface  of  the  ground  is  less  than  one-tenth  of  its 
weight  when  at  rest. 

Thus  the  trial  spins,  half  the  time  in  the  air, 
in  little  glides  of  fifty  to  a  hundred  feet,  increas- 
ing in  length,  give  practice,  practice,  PRACTICE, 
each  turn  of  the  field  making  the  sport  less  ex- 
citing and  fixing  the  controls  more  perfectly  in  the 
mind. 

THE  THIED  STAGE. — Thus  far  you  have  been 
turning  on  the  ground.  You  want  to  turn  in  the 
air.  Only  the  tail  control  was  required  while  on 
the  ground.  Now  two  things  are  required  after 
you  leave  the  ground  in  trying  to  make  a  turn: 
namely,  putting  the  tail  at  the  proper  angle,  and 
taking  charge  of  the  stabilizers,  because  in  mak- 
ing the  turn  in  the  air,  the  first  thing  which  will 
arrest  the  attention  will  be  the  tendency  of  the 
machine  to  turn  over  in  the  direction  that  you  are 
turning. 


178  AEROPLANES 

After  going  back  and  forth  in  straigtit-away 
glides,  until  you  have  perfect  confidence  and  full 
control,  comes  the  period  when  the  turns  should 
be  practiced  on.  These  should  be  long,  and  tried 
only  on  that  portion  of  the  field  where  you  have 
plenty  of  room. 

OBSERVATIONS  WHILE  IN  FLIGHT. — If  there  are 
any  bad  spots,  or  trees,  or  dangerous  places,  they 
should  be  spotted  out,  and  mentally  noted  before 
attempting  to  make  any  flight.  When  in  the  air 
during  these  trials  you  will  have  enough  to  oc- 
cupy your  mind  without  looking  out  for  the  haz- 
ardous regions  at  the  same  time. 

Make  the  first  turns  in  a  still  air.  If  you  should 
attempt  to  make  the  first  attempts  with  a  wind 
blowing  you  will  find  a  compound  motion  that  will 
very  likely  give  you  a  surprise.  In  making  the 
first  turn  you  will  get  the  sensation  of  trying  to 
fly  against  a  wind.  Assuming  that  you  are  turn- 
ing to  the  left,  it  will  have  the  sensation  of  a  wind 
coming  to  you  from  the  right. 

FLYING  IN  A  WIND. — Suppose  you  are  flying  di- 
rectly in  the  face  of  a  wind,  the  moment  you  begin 
to  turn  the  action,  or  bite  of  the  wind,  will  cause 
the  ends  of  the  planes  to  the  right  to  be  unduly 
elevated,  much  more  so  than  if  the  air  should  be 
calm.  This  raising  action  will  be  liable  to  startle 


EXPERIMENTAL  WORK  IN  FLYING     179 

you,  because  up  to  this  time  you  have  been  accus- 
tomed to  flying  along  in  a  straight  line. 

While  flying  around  at  the  part  of  the  circle 
where  the  wind  strikes  you  directly  on  the  right 
side  the  machine  has  a  tendency  to  climb,  and  you 
try  to  depress  the  forward  end,  but  as  soon  as  you 
reach  that  part  of  the  circle  where  the  winds  be- 
gin to  strike  on  your  back,  an  entirely  new  thing 
occurs. 

As  the  machine  is  now  traveling  with  the  wind, 
its  grip  on  the  air  is  less,  and  since  the  planes  were 
set  to  lower  the  machine,  at  the  first  part  of  the 
turn,  the  descent  will  be  pretty  rapid  unless  the 
angle  is  corrected. 

FIEST  TEIALS  IN  QUIET  ATMOSPHERE. — All  this 
would  be  avoided  if  the  first  trials  were  made  in 
a  quiet  atmosphere.  Furthermore,  you  will  be 
told  that  in  making  a  turn  the  machine  should  be 
pointed  downwardly,  as  though  about  to  make  a 
glide.  This  can  be  done  with  safety,  in  a  still 
air,  although  you  may  be  flying  low,  but  it  would 
be  exceedingly  dangerous  with  a  wind  blowing. 

MAKING  TURNS. — When  making  a  turn,  under  no 
circumstances  try  to  make  a  landing.  This 
should  never  be  done  except  when  flying  straight, 
and  then  safety  demands  that  the  landing  should 
be  made  against  the  wind  and  not  with  it.  There 


180  AEROPLANES 

are  two  reasons  for  this :  First,  when  flying  with 
the  wind  the  speed  must  be  greater  than  when  fly- 
ing against  it. 

By  greater  speed  is  meant  relative  to  the  earth. 
If  the  machine  has  a  speed  of  thirty  miles  an  hour, 
in  still  air,  the  speed  would  be  forty  miles  an  hour 
going  with  the  wind,  but  only  twenty  miles  against 
the  wind.  Second,  the  banking  of  the  planes 
against  the  air  is  more  effective  when  going  into 
the  wind  than  when  traveling  with  it,  and,  there- 
fore, the  speed  at  which  you  contact  with  the  earth 
is  lessened  to  such  an  extent  that  a  comparatively 
easy  landing  is  effected. 

THE  FOURTH  STAGE. — After  sufficient  time  has 
been  devoted  to  the  long  turns  shorter  turns  may 
be  made,  and  these  also  require  the  same  care, 
and  will  give  an  opportunity  to  use  the  lateral 
controls  to  a  greater  extent.  Begin  the  turns,  not 
by  an  abrupt  throw  of  the  turning  rudder,  but 
bring  it  around  gently,  correcting  the  turning 
movement  to  a  straight  course,  if  you  find  the 
machine  inclined  to  tilt  too  much,  until  you  get  used 
to  the  sensation  of  keeling  over.  Constant  prac- 
tice at  this  will  soon  give  confidence,  and  assure 
you  that  you  have  full  control  of  the  machine. 

THE  FIGURE  8. — You  are  now  to  increase  the 

height  of  flying,  and  this  involves  also  the  ability 

•  to  turn  in  the  opposite  direction,  so  that  you  may 


EXPERIMENTAL  WORK  IN  FLYING     181 

be  able  to  experience  the  sensation  of  using  the 
stabilizers  in  the  opposite  direction.  You  will 
find  in  this  practice  that  the  senses  must  take  in 
the  course  of  the  wind  from  two  quarters  now,  as 
you  attempt  to  describe  the  figure  8. 

This  is  a  test  which  is  required  in  order  to  ob- 
tain a  pilot's  license.  It  means  that  you  shall 
be  able  to  show  the  ability  to  turn  in  either  direc- 
tion with  equal  facility.  To  keep  an  even  flying 
altitude  while  describing  this  figure  in  a  wind,  is 
the  severest  test  that  can  be  exacted. 

THE  VOLPLANE. — This  is  the  technical  term  for 
a  glide.  Many  accidents  have  been  recorded  ow- 
ing to  the  stopping  of  the  motor,  which  in  the 
past  might  have  been  avoided  if  the  character  of 
the  glide  had  been  understood.  The  only  thing 
that  now  troubles  the  pilot  when  the  engine  "goes 
dead,"  is  to  select  a  landing  place. 

The  proper  course  in  such  a  case  is  to  urge 
the  machine  to  descend  as  rapidly  as  possible,  in 
order  to  get  a  headway,  for  the  time  being.  As 
there  is  now  no  propelling  force  the  glide  is  de- 
pended upon  to  act  as  a  substitute.  The  experi- 
enced pilot  will  not  make  a  straight-away  glide, 
but  like  the  vulture,  or  the  condor,  and  birds  of 
that  class,  soar  in  a  circle,  and  thus,  by  passing 
over  and  over  the  same  surfaces  of  the  earth,  en- 
able him  to  select  a  proper  landing  place. 


182  AEROPLANES 

THE  LANDING. — The  pilot  who  can  make  a  good 
landing  is  generally  a  good  flyer.  It  requires 
nicety  of  judgment  to  come  down  properly.  One 
thing  which  will  appear  novel  after  the  first  alti- 
tude flights  are  attempted  is  the  peculiar  sensa- 
tion of  the  apparently  increased  speed  as  the  earth 
comes  close  up  to  the  machine. 

At  a  height  of  one  hundred  feet,  flying  thirty 
miles  an  hour,  does  not  seem  fast,  because  the  sur- 
face of  the  earth  is  such  a  distance  away  that  par- 
ticular objects  remain  in  view  for  some  moments ; 
but  when  within  ten  feet  of  the  surface  the  same 
object  is  in  the  eye  for  an  instant  only. 

This  lends  a  sort  of  terror  to  the  novice.  He 
imagines  a  great  many  things,  but  forgets  some 
things  which  are  very  important  to  do  at  this 
time.  One  is,  that  the  front  of  the  machine  must 
be  thrown  up  so  as  to  bank  the  planes  against  the 
wind.  The  next  is  to  shut  off  the  power,  which 
is  to  be  done  the  moment  the  wheels  strike  the 
ground,  or  a  little  before. 

Upon  his  judgment  of  the  time  of  first  touching 
the  earth  depends  the  success  of  safely  alighting. 
He  may  bank  too  high,  and  come  down  on  the  tail 
with  disastrous  results.  If  there  is  plenty  of  field 
room  it  is  better  to  come  down  at  a  less  angle,  or 
even  keep  the  machine  at  an  even  keel,  and  the 
elevator  can  then  depress  the  tail  while  running 


EXPEKIMENTAL  WORK  IN  FLYING     183 

over  the  ground,  and  thus  bring  the  machine  to 
rest. 

Frequently,  when  about  to  land  the  machine 
will  rock  from  side  to  side.  In  such  a  case  it  is 
far  safer  to  go  up  into  the  air  than  to  make  the 
land,  because,  unless  the  utmost  care  is  exercised, 
one  of  the  wing  tips  will  strike  the  earth  and 
wreck  the  machine. 

Another  danger  point  is  losing  headway,  as  the 
earth  is  neared,  due  to  flying  at  too  flat  an  angle, 
or  against  a  wind  that  happens  to  be  blowing  par- 
ticularly hard  at  the  landing  place.  If  the  motor 
is  still  going  this  does  not  make  so  much  differ- 
ence, but  in  a  volplane  it  means  that  the  descent 
must  be  so  steep,  at  the  last  moment  of  flight,  that 
the  chassis  is  liable  to  be  crushed  by  the  impact. 

FLYING  ALTITUDE. — It  is  doubtful  whether  the 
disturbed  condition  of  the  atmosphere,  due  to 
the  contour  of  the  earth's  surface,  reaches  higher 
than  500  feet.  Over  a  level  area  it  is  certain  that 
it  is  much  less,  but  in  some  sections  of  the  coun- 
try, where  the  hill  ranges  extend  for  many  miles, 
at  altitudes  of  three  and  four  hundred  feet,  the 
upper  atmosphere  may  be  affected  for  a  thousand 
feet  above. 

Prof.  Lowe,  in  making  a  flight  with  a  balloon, 
from  Cincinnati  to  North  Carolina,  which  lasted 
a  day  and  all  of  one  night,  found  that  during  the 


184  AEROPLANES 

early  morning  the  balloon,  for  some  reason,  be- 
gan to  ascend,  and  climbed  nearly  five  thou- 
sand feet  in  a  few  hours,  and  as  unaccountably 
began  to  descend  several  hours  before  he  landed. 

Before  it  began  to  ascend,  he  was  on  the  west- 
ern side  of  the  great  mountain  range  which  ex- 
tends south  from  Pennsylvania  and  terminates  in 
Georgia.  He  was  actually  climbing  the  mountain 
in  a  drift  of  air  which  was  moving  eastwardly, 
and  at  no  time  was  he  within  four  thousand  feet 
of  the  earth  during  that  period,  which  shows  that 
air  movements  are  of  such  a  character  as  to  exert 
their  influence  vertically  to  great  heights. 

For  cross  country  flying  the  safest  altitude  is 
1000  feet,  a  distance  which  gives  ample  opportu- 
nity to  volplane,  if  necessary,  and  it  is  a  height 
which  enables  the  pilot  to  make  observations  of  the 
surface  so  as  to  be  able  to  judge  of  its  character. 

But  explanations  and  statements,  and  the  ex- 
periences of  pilots  might  be  detailed  in  pages,  and 
still  it  would  be  ineffectual  to  teach  the  art  of  fly- 
ing. The  only  sure  course  is  to  do  the  work  on 
an  actual  machine. 

Many  of  the  experiences  are  valuable  to  the 
learner,  some  are  merely  in  the  nature  of  cautions, 
and  it  is  advisable  for  the  beginner  to  learn  what 
the  experiences  of  others  Have  been,  although  they 
may  never  be  called  upon  to  duplicate  them. 


EXPERIMENTAL  WORK  IN  FLYING     185 

All  agree  that  at  great  elevations  the  flying 
conditions  are  entirely  different  from  those  met 
with  near  the  surface  of  the  ground,  and  the  his- 
tory of  accidents  show  that  in  every  case  where 
a  mishap  was  had  at  high  altitude  it  came  about 
through  defect  in  the  machine,  and  not  from  gusts 
or  bad  air  condition. 

On  the  other  hand,  the  uptilting  of  machines, 
the  accidents  due  to  the  so-called  "  Holes  in  the 
air,"  which  have  dotted  the  historic  pages  with 
accidents,  were  brought  about  at  low  altitudes. 

At  from  two  to  five  thousand  feet  the  air  may  be 
moving  at  speeds  of  from  twenty  to  forty  miles 
an  hour, — great  masses  of  winds,  like  the  trade 
stream,  which  are  uniform  over  vast  areas.  To 
the  aviator  flying  in  such  a  field,  with  the  earth 
hidden  from  him,  there  would  be  no  wind  to  indi- 
cate that  he  was  moving  in  any  particular  direc- 
tion. 

He  would  fly  in  that  medium,  in  any  direction, 
without  the  slightest  sense  that  he  was  in  a  gale. 
It  would  not  affect  the  control  of  the  machine, 
because  the  air,  though  moving  as  a  mass,  would 
be  the  same  as  flying  in  still  air.  It  is  only  when 
he  sees  fixed  objects  that  he  is  conscious  of  the 
movement  of  the  wind. 


CHAPTER  XIII 

THE   PROPELLER 

BY  far  the  most  difficult  problem  connected 
with  aviation  is  the  propeller.  It  is  the  one  great 
vital  element  in  the  science  and  art  pertaining  to 
this  subject  which  has  not  advanced  in  the  slight- 
est degree  since  the  first  machine  was  launched. 

The  engine  has  come  in  for  a  far  greater  share 
of  expert  experimental  work,  and  has  advanced 
most  rapidly  during  the  past  ten  years.  But, 
strange  to  say,  the  propeller  is,  essentially,  the 
same  with  the  exception  of  a  few  small  changes. 

PKOPELLER  CHANGES. — The  changes  which  have 
been  made  pertaining  to  the  form  of  structure, 
principally,  and  in  the  use  of  new  materials.  The 
kind  of  wood  most  suitable  has  been  discovered, 
but  the  lines  are  the  same,  and  nothing  has  been 
done  to  fill  the  requirement  which  grows  out  of 
the  difference  in  speed  when  a  machine  is  in  the 
act  of  launching  and  when  it  is  in  full  flight. 

PROPELLER  SHAPE. — It  cannot  be  possible  that 
the  present  shape  of  the  propeller  will  be  its  ulti- 
mate form.  It  is  inconceivable  that  the  propeller 

186 


THE  PROPELLER  187 

is  so  inefficient  that  only  one  sixty-fifth  of  the 
power  of  the  engine  is  available.  The  improve- 
ment in  propeller  efficiency  is  a  direction  which 
calls  for  experimental  work  on  the  part  of  inven- 
tors everywhere. 

The  making  of  a  propeller,  although  it  appears 
a  difficult  task,  is  not  as  complicated  as  would  ap- 
pear, and  with  the  object  in  view  of  making  the 
subject  readily  understood,  an  explanation  will  be 
given  of  the  terms  ''Diameter,"  and  " Pitch,"  as 
used  in  the  art. 

The  Diameter  has  reference  to  the  length  of 
the  propeller,  from  end  to  end.  In  calculating 
propeller  pull,  the  diameter  is  that  which  indi- 
cates the  speed  of  travel,  and  for  this  reason  is 
a  necessary  element. 

Thus,  for  instance,  a  propeller  three  feet  in 
diameter,  rotating  500  times  a  minute,  has  a  tip 
speed  of  1500  feet,  whereas  a  six  foot  propeller, 
rotating  at  the  same  speed,  moves  3000  feet  at  the 
tips. 

PITCH. — This  is  the  term  which  is  most  con- 
fusing, and  is  that  which  causes  the  most  frequent 
trouble  in  the  mind  of  the  novice.  The  term  will 
be  made  clear  by  carefully  examining  the  accom- 
panying illustration  and  the  following  descrip- 
tion: 

In  Fig.  76  is  shown  a  side  view  of  a  propeller 


188 


AEROPLANES 


A,  mounted  on  a  shaft  B,  which  is  free  to  move 
longitudinally.  Suppose  we  turn  the  shaft  so  the 
tip  will  move  along  on  the  line  indicated  by  the 
arrow  C. 

Now  the  pitch  of  the  blade  at  D  is  such  that  it 
will  be  exactly  in  line  with  the  spirally-formed 


Z,  inc. 


course  E,  for  one  complete  turn.  As  the  propeller 
shaft  has  now  advanced,  along  the  line  E,  and 
stopped  after  one  turn,  at  F,  the  measure  between 
the  points  F  and  G  represents  the  pitch  of  the  pro- 
peller. Another  way  to  express  it  would  be  to 
call  the  angle  of  the  blade  a  five,  or  six,  or  a  seven 
foot  pitch,  as  the  pitches  are  measured  in  feet. 


THE  PEOPELLER  189 

In  the  illustration  thus  given  the  propeller  shaft, 
having  advanced  six  feet,  we  have  what  is  called 
a  six  foot  pitch. 

Now,  to  lay  out  such  a  pitch  is  an  easy  matter. 
Assume,  as  in  Fig.  77,  that  A  represents  the  end 
of  the  blank  from  which  the  propeller  is  to  be  cut, 
and  that  the  diameter  of  this  blank,  or  its  length 
from  end  to  end  is  seven  feet.  The  problem  now 
is  to  cut  the  blades  at  such  an  angle  that  we  shall 
have  a  six  foot  pitch. 

7/Z. 


y  * 

Ci?-cuMfere?ve  =  3.  M/6X7 

e& 


.  77. 


LAYING  OUT  THE  PITCH.  —  First,  we  must  get  the 
circumference  of  the  propeller,  that  is,  the  dis- 
tance the  tip  of  the  propeller  will  travel  in  making 
one  complete  turn.  This  is  done  by  multiplying 
7  by  3.1416.  This  equals  21.99,  or,  practically,  22 
feet. 

A  line  B  is  drawn,  extending  out  horizontally 
along  one  side  of  the  blank  A,  this  line  being  made 
on  a  scale,  to  represent  22  feet.  Secondly,  at  the 
end  of  this  line  drawn  a  perpendicular  line  C,  6 


190  AEROPLANES 

feet  long.  A  perpendicular  line  is  always  one 
which  is  at  right  angles  to  a  base  line.  In  this 
case  B  is  the  base  line. 

Line  C  is  made  6  feet  long,  because  we  are  try- 
ing to  find  the  angle  of  a  6  foot  pitch.  If,  now,  a 
line  D  is  drawn  from  the  ends  of  the  two  lines  B, 
C,  it  will  represent  the  pitch  which,  marked  across 
the  end  of  the  blank  A,  will  indicate  the  line  to  cut 
the  blade. 

PITCH  RULE. — The  rule  may,  therefore,  be 
stated  as  follows:  Multiply  the  diameter  (in 
feet)  of  the  propeller  by  3.1416,  and  draw  a  line 
the  length  indicated  by  the  product.  At  one  end 
of  this  line  draw  a  perpendicular  line  the  length 
of  the  pitch  requirement  (in  feet),  and  join  the 
ends  of  the  two  lines  by  a  diagonal  line,  and  this 
line  will  represent  the  pitch  angle. 

Propellers  may  be  made  of  wood  or  metal,  the 
former  being  preferred  for  the  reason  that  this 
material  makes  a  lighter  article,  and  is  stronger, 
in  some  respects,  than  any  metal  yet  suggested. 

LAMINATED  CONSTRUCTION. — All  propellers 
should  be  laminated, — that  is,  built  up  of  layers 
of  wood,  glued  together  and  thoroughly  dried, 
from  which  the  propeller  is  cut. 

A  product  thus  made  is  much  more  serviceable 
than  if  made  of  one  piece,  even  though  the  lami- 
nated parts  are  of  the  same  wood,  because  the 


THE  PROPELLER  191 

different  strips  used  will  have  their  fibers  over- 
lapping each  other,  and  thus  greatly  augment  the 
strength  of  the  whole. 

Generally  the  alternate  strips  are  of  different 
materials,  black  walnut,  mahogany,  birch,  spruce, 
and  maple  being  the  most  largely  used,  but  ma- 
hogany and  birch  seem  to  be  mostly  favored. 

LAYING  UP  A  PROPELLER  FORM. — The  first  step 
necessary  is  to  prepare  thin  strips,  each,  say, 
seven  feet  long,  and  five  inches  wide,  and  three- 
eighths  of  an  inch  thick.  If  seven  such  pieces  are 


put  together,  as  in  Fig.  78,  it  will  make  an  assem- 
blage of  two  and  five-eighth  inches  high. 

Bore  a  hole  centrally  through  the  assemblage, 
and  place  therein  a  pin  B.  The  contact  faces  of 
these  strips  should  be  previously  well  painted 
over  with  hot  glue  liberally  applied.  When  they 
are  then  placed  in  position  and  the  pin  is  in  place, 
the  ends  of  the  separate  pieces  are  offset,  one  be- 
yond the  other,  a  half  inch,  as  shown,  for  instance, 
in  Fig.  79. 

This  will  provide  ends  which  are  eight  and  a 
half  inches  broad,  and  thus  furnish  sufficient  ma- 


192 


AEROPLANES 


terial  for  the  blades.  The  mass  is  then  subjected 
to  heavy  pressure,  and  allowed  to  dry  before  the 
blades  are  pared  down. 


.  79. 


MAKING  WIDE  BLADES.  —  If  a  wider  blade  is  de- 
sired, a  greater  number  of  steps  may  be  made  by 
adding  the  requisite  number  of  strips;  or,  the 
strips  may  be  made  thicker.  In  many  propellers, 
not  to  exceed  four  different  strips  are  thus  glued 
together.  The  number  is  optional  with  the 
maker. 

An  end  view  of  such  an  assemblage  of  strips 
is  illustrated  in  Fig.  80.  The  next  step  is  to  lay 


8O. 


off  the  pitch,  the  method  of  obtaining  which  has 
been  explained. 

Before  starting  work  the  sides,  as  well  as  the 
ends,  should  be  marked,  and  care  observed  to 


THE  PROPELLER 


193' 


place  a  distinctive  mark  on  the  front  side  of  the 
propeller. 

Around   the  pin  B,   Fig.   81,  make   S-shaped 
marks  C,  to  indicate  where  the  cuts  on  the  faces 


of  the  blades  are  to  begin.  Then  on  the  ends  of 
the  block  scribe  the  pitch  angle,  which  is  indi- 
cated by  the  diagonal  line  D,  Fig.  80. 

This  line  is  on  the  rear  side  of  the  propeller, 
and  is  perfectly  straight.  Along  the  front  of  this 
line  is  a  bowline  E,  which  indicates  the  front  sur- 
face of  the  propeller  blade. 

PROPELLER    OUTLINE. — While    the    marks    thus 


given  show  the  angles,  and  are  designed  to  indi- 
cate the  two  faces  of  the  blades,  there  is  still  an- 
other important  element  to  be  considered,  and 
that  is  the  final  outline  of  the  blades. 


194  AEROPLANES 

It  is  obvious  that  the  outline  may  be  varied 
so  that  the  entire  width  at  1,  Fig.  82,  may  be  used, 
or  it  may  have  an  outline,  as  represented  by  the 
line  2,  in  this  figure,  so  that  the  widest  part  will 
be  at  or  near  the  dotted  line  3,  say  two-thirds  of 
the  distance  from  the  center  of  the  blade. 

This  is  the  practice  with  most  of  the  manufac- 
turers at  the  present  time,  and  some  of  them 
claim  that  this  form  produces  the  best  results. 

FOB  HIGH  SPEEDS. — Fig.  83  shows  a  propeller 
cut  from  a  blank,  4"x6"  in  cross  section,  not 
laminated. 


.  <3&  Cut  from  a 


It  should  be  borne  in  mind  that  for  high  speeds 
the  blades  must  be  narrow.  A  propeller  seven 
feet  in  diameter  with  a  six  foot  pitch,  turning 
950  revolutions  per  minute,  will  produce  a  pull  of 
350  pounds,  if  properly  made. 

Such  a  propeller  can  be  readily  handled  by  a 
forty  horse  power  motor,  such  as  are  specially 
constructed  for  flying  machine  purposes. 

INCREASING  PROPELLER  EFFICIENCY.  —  Some  ex- 
periments have  been  made  lately,  which,  it  is 
claimed,  largely  increase  the  efficiency  of  propel- 


THE  PKOPELLEB  195 

lers.  The  improvement  is  directed  to  the  outline 
shape  of  the  blade. 

The  typical  propeller,  such  as  we  have  illus- 
trated, is  one  with  the  wide  part  of  the  blade  at 
the  extremity.  The  new  type,  as  suggested,  re- 
verses this,  and  makes  the  wide  part  of  the  blade 
near  the  hub,  so  that  it  gradually  tapers  down  to 
a  narrow  tip. 

Such  a  form  of  construction  is  shown  in  Fig. 
84.  This  outline  has  some  advantages  from  one 


standpoint,  namely,  that  it  utilizes  that  part  of 
the  blade  near  the  hub,  to  produce  a  pull,  and 
does  not  relegate  all  the  duty  to  the  extreme  ends 
or  tips. 

To  understand  this  more  fully,  let  us  take  a 
propeller  six  feet  in  diameter,  and  measure  the 
pull  or  thrust  at  the  tips,  and  also  at  a  point  half 
way  between  the  tip  and  the  hub. 

In  such  a  propeller,  if  the  blade  is  the  same 
width  and  pitch  at  the  two  points  named,  the  pull 
at  the  tips  will  be  four  times  greater  than  at  the 
intermediate  point. 


CHAPTER  XIV 

EXPERIMENTAL   GLIDERS  AND  MODEL  AEROPLANES 

AN  amusing  and  very  instructive  pastime  is 
afforded  by  constructing  and  flying  gliding  ma- 
chines, and  operating  model  aeroplanes,  the  latter 
being  equipped  with  their  own  power. 

Abroad  this  work  has  been  very  successful  as 
a  means  of  interesting  boys,  and,  indeed,  men 
who  have  taken  up  the  science  of  aviation  are 
giving  this  sport  serious  thought  and  study. 

When  a  machine  of  small  dimensions  is  made 
the  boy  wonders  why  a  large  machine  does  not 
bear  the  same  relation  in  weight  as  a  small  ma- 
chine. This  is  one  of  the  first  lessons  to  learn. 

THE  RELATION  OF  MODELS  TO  FLYING  MACHINES. 
— A  model  aeroplane,  say  two  feet  in  length,  which 
has,  we  will  assume,  50  square  inches  of  support- 
ing surface,  seems  to  be  a  very  rigid  structure, 
in  proportion  to  its  weight.  It  may  be  dropped 
from  a  considerable  height  without  injuring  it, 
since  the  weight  is  only  between  two  and  three 
ounces. 

An  aeroplane  twenty  times  the  length  of  this 

196 


MODEL  AEROPLANES  197 

model,  however  strongly  it  may  be  made,  if 
dropped  the  same  distance,  would  be  crushed,  and 
probably  broken  into  fragments. 

If  the  large  machine  is  twenty  times  the  dimen- 
sions of  the  small  one,  it  would  be  forty  feet  in 
length,  and,  proportionally,  would  have  only 
seven  square  feet  of  sustaining  surface.  But  an 
operative  machine  of  that  size,  to  be  at  all  rigid, 
would  require  more  than  twenty  times  the  ma- 
terial in  weight  to  be  equal  in  strength. 

It  would  weigh  about  800  pounds,  that  is,  4800 
times  the  weight  of  the  model,  and  instead  of 
having  twenty  times  the  plane  surface  would  re- 
quire one  thousand  times  the  spread. 

It  is  this  peculiarity  between  models  and  the 
actual  flyers  that  for  years  made  the  question  of 
flying  a  problem  which,  on  the  basis  of  pure  cal- 
culation alone,  seemed  to  offer  a  negative;  and 
many  scientific  men  declared  that  practical  flying 
was  an  impossibility. 

LESSONS  FROM  MODELS. — Men,  and  boys,  too, 
can  learn  a  useful  lesson  from  the  model  aero- 
planes in  other  directions,  however,  and  the  prin- 
cipal thing  is  the  one  of  stability. 

When  everything  is  considered  the  form  or 
shape  of  a  flying  model  will  serve  to  make  a  large 
flyer.  The  manner  of  balancing  one  will  be  a 
good  criterion  for  the  other  in  practice,  and  ex- 


198  ,  AEROPLANES 

perimenting  with  these  small  devices  is,  there- 
fore, most  instructive. 

The  difference  between  gliders  and  model  aero- 
planes is,  that  gliders  must  be  made  much  lighter 
because  they  are  designed  to  be  projected  through 
the  air  by  a  kick  of  some  kind. 

FLYING  MODEL  AEROPLANES. — Model  aeroplanes 
contain  their  own  power  and  propellers  which, 
while  they  may  run  for  a  few  seconds  only,  serve 
the  purpose  of  indicating  how  the  propeller  will 
act,  and  in  what  respect  the  sustaining  surfaces 
are  efficient  and  properly  arranged. 

It  is  not  our  purpose  to  give  a  treatise  on  this 
subject  but  to  confine  this  chapter  to  an  exposi- 
tion of  a  few  of  the  gliders  and  model  forms  which 
are  found  to  be  most  efficient  for  experimental 
work. 

AN  EFFICIENT  GLIDER. — Probably  the  simplest 
and  most  efficient  glider,  and  one  which  can  be 
made  in  a  few  moments,  is  to  make  a  copy  of  the 
deltoid  kite,  previously  referred  to. 

This  is  merely  a  triangularly-shaped  piece  of 
paper,  or  stiff  cardboard  A,  Fig.  84,  creased  in 
the  middle,  along  the  dotted  line  B,  the  side  wings 
C,  C,  being  bent  up  so  as  to  form,  what  are  called 
diedral  angles.  This  may  be  shot  through  the 
air  by  a  flick  of  the  finger,  with  the  pointed  end 
foremost,  when  used  as  a  glider. 


MODEL  AEROPLANES 


199 


THE  DELTOID  FORMATION. — This  same  form  may 
be  advantageously  used  as  a  model  aeroplane,  but 
in  that  case  the  broad  end  should  be  foremost. 


Tt&ltoid  Jlacer. 


Fig.  86  shows  the  deltoid  glider,  or  aeroplane, 
with  three  cross  braces,  A,  B,  C,  in  the  two  for- 
ward braces  of  which  are  journaled  the  propeller 


200  AEROPLANES 

shaft  D,  so  that  the  propeller  E  is  at  the  broad 
end  of  the  glider. 

A  short  stem  F  through  the  rear  brace  C,  pro- 
vided with  a  crank,  has  its  inner  end  connected 
with  the  rear  end  of  the  shaft  D  by  a  rubber  band 
G,  by  which  the  propeller  is  driven. 

A  tail  may  be  attached  to  the  rear  end,  or  at 
the  apex  of  the  planes,  so  it  can  be  set  for  the 
purpose  of  directing  the  angle  of  flight,  but  it  will 
be  found  that  this  form  has  remarkable  stability 
in  flight,  and  will  move  forwardly  in  a  straight 
line,  always  making  a  graceful  downward  move- 
ment when  the  power  is  exhausted. 

It  seems  to  be  a  form  which  has  equal  sta- 
bilizing powers  whether  at  slow  or  at  high  speeds, 
thus  differing  essentially  from  many  forms  which 
require  a  certain  speed  in  order  to  get  the  best 
results. 

RACING  MODELS. — Here  and  in  England  many 
racing  models  have  been  made,  generally  of  the 
A-shaped  type,  which  will  be  explained  herein- 
after. Such  models  are  also  strong,  and  able  to 
withstand  the  torsional  strain  required  by  the 
rubber  which  is  used  for  exerting  the  power. 

It  is  unfortunate  that  there  is  not  some  type  of 
cheap  motor  which  is  light,  and  adapted  to  run 
for  several  minutes,  which  would  be  of  great  value 
in  work  of  this  kind,  but  in  the  absence  of  such 


MODEL  AEROPLANES 


201 


mechanism  rubber  bands  are  found  to  be  most 
serviceable,  giving  better  results  than  springs  or 
bows,  since  the  latter  are  both  too  heavy  to  be 
available,  in  proportion  to  the  amount  of  power 
developed. 

Unlike  the  large  aeroplanes,  the  supporting 
surfaces,  in  the  models,  are  at  the  rear  .end  of 
the  frames,  the  pointed  ends  being  in  front. 


.  87.  A- 


ftacznti  aiteter. 


Fig.  87  shows  the  general  design  of  the  A- 
shaped  gliding  plane  or  aeroplane.  This  is  com- 
posed of  main  frame  pieces  A,  A,  running  fore 
and  aft,  joined  at  their  rear  ends  by  a  cross  bar 
B,  the  ends  of  which  project  out  slightly  beyond 
their  juncture  with  the  side  bars  A,  A.  These 


202  AEKOPLANES 

projecting  ends  have  holes  drilled  therein  to  re- 
ceive the  shafts  C,  C,  of  the  propeller  D,  D. 

A  main  plane  E  is  mounted  transversely  across 
this  frame  at  its* rear  end,  while  at  its  forward 
end  is  a  small  plane,  called  the  elevator.  The 
pointed  end  of  the  frame  has  on  each  side  a  turn- 
buckle  G,  for  the  purpose  of  winding  up  the  shaft, 
and  thus  twisting  the  propeller,  although  this  is 
usually  dispensed  with,  and  the  propeller  itself 
is  turned  to  give  sufficient  twist  to  the  rubber  for 
this  purpose. 

THE  POWER  FOE  MODEL  AEROPLANES. — One  end 
of  the  rubber  is  attached  to  the  hook  of  the  shaft 
C,  and  the  other  end  to  the  hook  or  to  the  turn- 
buckle  G,  if  it  should  be  so  equipped. 

The  rubbers  are  twisted  in  opposite  directions, 
to  correspond  with  the  twist  of  the  propeller 
blades,  and  when  the  propellers  are  permitted  to 
turn,  their  grip  on  the  air  will  cause  the  model  to 
shoot  forwardly,  until  the  rubbers  are  untwisted, 
when  the  machine  will  gradually  glide  to  the 
ground. 

MAKING  THE  PROPELLER. — These  should  have 
the  pitch  uniform  on  both  ends,  and  a  simple 
little  device  can  be  made  to  hold  the  twisted  blade 
after  it  has  been  steamed  and  bent.  Birch  and 
holly  are  good  woods  for  the  blades.  The  strips 
should  be  made  thin  and  then  boiled,  or,  what  is 


MODEL  AEROPLANES 


203 


better  still,  should  be  placed  in  a  deep  pan,  and 
held  on  a  grid  above  the  water,  so  they  will  be 
thoroughly  steamed. 

They  are  then  taken  out  and  bent  by  hand,  or 
secured  between  a  form  specially  prepared  for 
the  purpose.  The  device  shown  in  Fig.  88  shows 
a  base  board  which  has  in  the  center  a  pair  of 
parallel  pins  A,  A,  slightly  separated  from  each 
other. 


At  each  end  of  the  base  board  is  a  pair  of  holes 
C,  D,  drilled  in  at  an  angle,  the  angles  being  the 
pitch  desired  for  the  ends  of  the  propeller.  In 
one  of  these  holes  a  pin  E  is  placed,  so  the  pins 
at  the  opposite  ends  project  in  different  direc- 
tions, and  the  tips  of  the  propeller  are  held 
against  the  ends  of  these  pins,  while  the  middle 
of  the  propeller  is  held  between  the  parallel  pins 
A,  A. 

The  two  holes,  at  the  two  angles  at  the  ends  of 


204  AEROPLANES 

the  board,  are  for  the  purpose  of  making  right 
and  left  hand  propellers,  as  it  is  desirable  to  use 
two  propellers  with  the  A-shaped  model.  Two 
propellers  with  the  deltoid  model  are  not  so  nec- 
essary. 

After  the  twist  is  made  and  the  blade  properly 
secured  in  position  it  should  be  allowed  to  thor- 
oughly dry,  and  afterwards,  if  it  is  coated  with 
shellac,  will  not  untwist,  as  it  is  the  changing 
character  of  the  atmosphere  which  usually  causes 
the  twisted  strips  to  change  their  positions. 
Shellac  prevents  the  moist  atmosphere  from  af- 
fecting them. 

MATERIAL  FOR  PROPELLERS. — Very  light  propel- 
lers can  also  be  made  of  thin,  annealed  aluminum 
sheets,  and  the  pins  in  that  case  will  serve  as 
guides  to  enable  you  to  get  the  desired  pitch. 
Fiber  board  may  also  be  used,  but  this  is  more 
difficult  to  handle. 

Another  good  material  is  celluloid  sheets, 
which,  when  cut  into  proper  strips,  is  dipped  in 
hot  water,  for  bending  purposes,  and  it  readily 
retains  its  shape  when  cooled. 

RUBBER, — Suitable  rubber  for  the  strips  are 
readily  obtainable  in  the  market.  Experiment 
will  soon  show  what  size  and  lengths  are  best 
adapted  for  the  particular  type  of  propellers 
which  you  succeed  in  making. 


MODEL  AEROPLANES 


205 


PROPELLEE  SHAPE  AND  SIZE. — A  good  propor- 
tion of  propeller  is  shown  in  Fig.  89.  This  also 
shows  the  form  and  manner  of  connecting  the 
shaft.  The  latter  A  has  a  hook  B  on  one  end  to 
which  the  rubber  may  be  attached,  and  its  other 
end  is  flattened,  as  at  C,  and  secured  to  the  blade 
by  two-pointed  brads  D,  clinched  on  the  other 
side. 


89.  tihae  and 


The  collar  E  is  soldered  on  the  shaft,  and  in 
practice  the  shaft  is  placed  through  the  bearing 
hole  at  the  end  of  the  frame  before  the  hook  is' 
bent. 

SUPPORTING  SURFACES.  —  The  supporting  sur- 
faces may  be  made  perfectly  flat,  although  in  this 
particular  it  would  be  well  to  observe  the  rules 
with  respect  to  the  camber  of  large  machines. 


CHAPTER  XV 

THE  AEROPLANE   IN   THE   GEEAT   WAR 

DURING  the  civil  war  the  Federal  forces  used 
captive  balloons  for  the  purpose  of  discovering 
the  positions  of  the  enemy.  They  were  of  great 
service  at  that  time,  although  they  were  stationed 
far  within  the  lines  to  prevent  hostile  guns  from 
reaching  them. 

BALLOON  OBSERVATIONS. — Necessarily,  observa- 
tions from  balloons  were  and  are  imperfect.  It 
was  found  to  be  very  unsatisfactory  during  the 
Russian-Japanese  war,  because  the  angle  of  vision 
is  very  low,  and,  furthermore,  at  such  distances  the 
movements,  or  even  the  location  of  troops  is  not 
^  observable,  except  under  the  most  favorable  con- 
ditions. 

Balloon  observation  during  the  progress  of  a 
battle  is  absolutely  useless,  because  the  smoke 
from  the  firing  line  is,  necessarily,  between  the 
balloon  and  the  enemy,  so  that  the  aerial  scout 
has  no  opportunity  to  make  any  observations,  even 
in  detached  portions  of  the  fighting  zone,  which 
are  of  any  value  to  the  commanders. 

206 


AEROPLANE  IN  THE  GREAT  WAR     207 

CHANGED  CONDITIONS  OF  WAEFAEE. — Since  our 
great  war,  conditions  pertaining  to  guns  have  been 
revolutionized.  Now  the  ranges  are  so  great  that 
captive  balloons  would  have  to  be  located  far  in 
the  rear,  and  at  such  a  great  distance  from  the 
firing  line  that  even  the  best  field  glasses  would 
be  useless. 

The  science  of  war  has  also  evolved  another 
condition.  Soldiers  are  no  longer  exposed  dur- 
ing artillery  attacks.  Uniforms  are  made  to  imi- 
tate natural  objects.  The  khaki  suits  were  de- 
signed to  imitate  the  yellow  veldts  of  South  Af- 
rica; the  gray-green  garments  of  the  German 
forces  are  designed  to  simulate  the  green  fields 
of  the  north. 

THE  EFFOET  TO  CONCEAL  COMBATANTS. — The 
French  have  discarded  the  historic  red  trousers, 
and  the  elimination  of  lace,  white  gloves,  and 
other  telltale  insignias  of  the  officers,  have  been 
dispensed  with  by  special  orders. 

In  the  great  European  war  armies  have  bur- 
rowed in  the  earth  along  battle  lines  hundreds  of 
miles  in  length ;  made  covered  trenches ;  prepared 
artificial  groves  to  conceal  batteries,  and  in  many 
ingenious  ways  endeavored  to  make  the  battle- 
field an  imitation  field  of  nature. 

SMOKELESS  POWDEB. — While  smokeless  powder 
has  been  utilized  to  still  further  hide  a  fighting 


208  AEROPLANES 

• 
force,  it  has,  in  a  measure,  uncovered  itself,  as 

the  battlefield  is  not  now,  as  in  olden  times,  over- 
spread with  masses  of  rolling  smoke. 

Nevertheless,  over  every  battlefield  there  is  a 
haze  which  can  be  penetrated  only  from  above, 
hence  the  possibilities  of  utilizing  the  aeroplane 
in  war  became  the  most  important  study  with  all 
nations,  as  soon  as  flying  became  an  accomplished 
fact. 

INVENTIONS  TO  ATTACK  AERIAL  CRAFT. — Before 
any  nation  had  the  opportunity  to  make  an  actual 
test  on  the  battlefield,  inventors  were  at  work  to 
devise  a  means  whereby  an  aerial  foe  could  be 
met.  In  a  measure  the  aerial  gun  has  been  suc- 
cessful, but  months  of  war  has  shown  that  the 
aeroplane  is  one  of  the  strongest  arms  of  the 
service  in  actual  warfare. 

It  was  assumed  prior  to  the  European  war  that 
the  chief  function  of  the  aeroplane  would  be  the 
dropping  of  bombs, — that  is  for  service  in  at- 
tacking a  foe.  Actual  practice  has  not  justified 
this  theory.  In  some  places  the  appearance  of 
the  aeroplane  has  caused  terror,  but  it  has  been 
found  the  great  value  is  its  scouting  advantages. 

FUNCTION  OF  THE  AEROPLANE  IN  WAR. — While 
bomb  throwing  may  in  the  future  be  perfected, 
it  is  not  at  all  an  easy  problem  for  an  aviator  to 
do  work  which  is  commensurate  with  the  risk  in- 


AEROPLANE  IN  THE  GREAT  WAR     209 

volved.  The  range  is  generally  too  great;  the 
necessity  of  swift  movement  in  the  machine  too 
speedy  to  assure  accuracy,  and  to  attack  a  foe  at 
haphazard  points  can  never  be  effectual.  Even 
the  slowly-moving  gas  fields,  like  the  Zeppelin, 
cannot  deliver  bombs  with  any  degree  of  preci- 
sion or  accuracy. 

BOMB-THROWING  TESTS. — It  is  interesting,  how- 
ever, to  understand  how  an  aviator  knows  where 
or  when  to  drop  the  bomb  from  a  swiftly-moving 
machine.  Several  things  must  be  taken  into  con- 
sideration, such  as  the  height  of  the  machine  from 
the  earth ;  its  speed,  and  the  parabolic  curve  that 
the  bomb  will  take  on  its  flight  to  the  earth. 

When  an  object  is  released  from  a  moving  ma- 
chine it  will  follow  the  machine  from  which  it  is 
dropped,  gradually  receding  from  it,  as  it  de- 
scends, so  that  the  machine  is  actually  beyond 
the  place  where  the  bomb  strikes  the  earth,  due 
to  the  retarding  motion  of  the  atmosphere  against 
the  missile. 

The  diagram  Fig.  90  will  aid  the  boy  in  grasp- 
ing the  situation.  A  is  the  airship;  B  the  path 
of  its  flight;  C  the  course  of  the  bomb  after  it 
leaves  the  airship;  and  D  the  earth.  The  ques- 
tion is  how  to  determine  the  proper  movement 
when  to  release  the  bomb. 

METHOD    FOR    DETERMINING    MOVEMENT    OF    A 


210  AEROPLANES 

BOMB.— Lieut.  Scott,  U.  S.  A.,  of  the  Coast  Sur- 
vey Artillery,  suggested  a  method  for  determin- 
ing these  questions.  It  was  necessary  to  ascer- 
tain, first,  the  altitude  and  speed.  While  the  ba- 
rometer is  used  to  determine  altitudes,  it  is 
obvious  that  speed  is  a  matter  much  more  diffi- 
cult to  ascertain,  owing  to  the  wind  movements, 
which  in  all  cases  make  it  difficult  for  a  flier  to 

Course  of  dTiip. 
oirib 


^  tff  90.  Course  of&  Bomb 

determine,  even  with  instruments  which  have 
been  devised  for  the  purpose. 

Instead,  therefore,  of  relying  on  the  barometer, 
the  ship  is  equipped  with  a  telescope  which  may 
be  instantly  set  at  an  angle  of  45  degrees,  or  ver- 
tically. 

Thus,  Fig  91  shows  a  ship  A,  on  which  is 
mounted  a  telescope  B,  at  an  angle  of  45  degrees. 


AEROPLANE  IN  THE  GREAT  WAR     211 

The  observer  first  notes  the  object  along  the  line 
of  45  degrees,  and  starts  the  time  of  this  observa- 
tion by  a  stop  watch. 

The  telescope  is  then  turned  so  it  is  vertical, 
as  at  C,  and  the  observer  watches  through  the 
telescope  until  the  machine  passes  directly  over 


97-  jyete7Minzsi$  Altitude  cuidd&eecl. 


the  object,  when  the  watch  is  stopped,  to  indicate 
the  time  between  the  two  observations. 

The  height  of  the  machine  along  the  line  D  is 
thus  equal  to  the  line  E  from  B  to  C,  and  the  time 
of  the  flight  from  B  to  C  being  thus  known,  as 
well  as  the  height  of  the  machine,  the  observer 
consults  specially-prepared  tables  which  show 


212  AEROPLANES 

just  what  kind  of  a  curve  the  bomb  will  make  at 
that  height  and  speed. 

All  that  is  necessary  now  is  to  set  the  sighter 
of  the  telescope  at  the  angle  given  in  the  tables, 
and  when  the  object  to  be  hit  appears  at  the  sight, 
the  bomb  is  dropped. 

THE  GKEAT  EXTENT  OP  MODEEN  BATTLE  LINES. — 
The  great  war  brought  into  the  field  such  stu- 
pendous masses  of  men  that  the  battle  lines  have 
extended  over  an  unbroken  front  of  over  200 
miles. 

In  the  battle  of  Waterloo,  about  140,000  men 
were  engaged  on  both  sides,  and  the  battle  front 
was  less  than  six  miles.  There  were,  thus  massed, 
along  the  front,  over  20,000  men  every  mile  of 
the  way,  or  10,000  on  each  side. 

In  the  conflict  between  the  Allies  and  the  Ger- 
mans it  is  estimated  that  there  were  less  than 
7500  along  each  mile.  It  was  predicted  in  the 
earlier  stages  of  the  war  that  it  would  be  an  easy 
matter  for  either  side  to  suddenly  mass  such  an 
overwhelming  force  at  one  point  as  to  enable  the 
attacking  party  to  go  through  the  opposing  force 
like  a  wedge. 

Such  tactics  were  often  employed  by  Napoleon 
and  other  great  masters  of  war ;  but  in  every  ef- 
fort where  it  has  been  attempted  in  the  present 
conflict,  it  was  foiled. 


AEROPLANE  IN  THE  GREAT  WAR  213 

The  opposing  force  was  ready  to  meet  the  at- 
tack with  equal  or  superior  numbers.  The  eye 
of  the  army,  the  aeroplane,  detected  the  movements 
in  every  instance. 

THE  AEROPLANE  DETECTING  THE  MOVEMENTS  OF 
ABMIES. — In  the  early  stages  of  the  war,  when 
the  Germans  drove  the  left  of  the  French  army 
towards  Paris,  the  world  expected  an  investment 
of  that  city.  Suddenly,  and  for  no  apparent 
reason,  the  German  right  was  forced  back  and 
commenced  to  retreat. 

It  was  not  known  until  weeks  afterwards  that 
the  French  had  assembled  a  large  army  to  the 
west  and  northwest  of  Paris,  ready  to  take  the 
Germans  in  flank  the  moment  an  attempt  should 
be  made  to  encircle  the  Paris  forts. 

The  German  aviators  discovered  the  hidden 
army,  and  it  is  well  for  them  that  they  did 
so,  for  it  is  certain  if  they  had  surrounded  the 
outlying  forts,  it  would  have  been  an  easy  matter 
for  the  concealed  forces  to  destroy  their  com- 
munications, and  probably  have  forced  the  sur- 
render of  a  large  part  of  the  besiegers. 

The  aeroplane  in  warfare,  therefore,  has  con- 
stantly noted  every  disposition  of  troops,  located 
the  positions  and  judged  the  destination  of  con- 
voys; the  battery  emplacements;  and  the  direc- 
tion in  which  large  forces  have  been  moved  from 


214  AEROPLANES 

one  part  of  the  line  to  the  other,  thus  keeping  the 
commanders  so  well  informed  that  few  surprises 
were  possible. 

THE  EFFECTIVE  HEIGHT  FOE  SCOUTING. — It  has 
been  shown  that  aeroplane  scouting  is  not  effec- 
tive at  high  altitudes.  It  is  not  difficult  for  avia- 
tors to  reach  and  maintain  altitudes  of  five  thou- 
sand feet  and  over,  but  at  that  elevation  it  is  im- 
possible to  distinguish  anything  but  the  movement 
of  large  forces. 

SIZES  OF  OBJECTS  AT  GBEAT  DISTANCES. — At  a 
distance  of  one  mile  an  automobile,  twenty  feet 
in  length,  is  about  as  large  as  a  piece  of  pencil 
one  inch  long,  viewed  at  a  distance  of  thirty-five 
feet.  A  company  of  one  hundred  men,  which  in 
marching  order,  say  four  abreast,  occupies  a  space 
of  eight  by  one  hundred  feet,  looks  to  the  aviator 
about  as  large  as  an  object  one  inch  in  length,  four 
and  a  half  feet  from  the  eye. 

The  march  of  such  a  body  of  men,  viewed  at 
that  distance,  is  so  small  as  almost  to  be  imper- 
ceptible to  the  eye  of  an  observer  at  rest.  How 
much  more  difficult  it  is  to  distinguish  a  move- 
ment if  the  observer  is  in  a  rapidly-moving  ma- 
chine. 

For  these  reasons  observations  must  be  made 
at  altitudes  of  less  than  a  mile,  and  the  hazard 
of  these  enterprises  is,  therefore,  very  great, 


AEEOPLANE  IN  THE  GBEAT  WAR     215 

since  the  successful  scout  must  bring  himself 
within  range  of  specially  designed  guns,  which 
are  effective  at  a  range  of  3000  yards  or  more, 
knowing  that  his  only  hope  of  safety  lies  in  the 
chance  that  the  rapidly-moving  machine  will  avoid 
the  rain  of  bullets  that  try  to  seek  him  out. 

SOME  DARING  FEATS  IN  WAR. — It  would  be  im- 
possible to  recount  the  many  remarkable  aerial 
fights  which  have  taken  place  in  the  great  war. 
Some  of  them  seem  to  be  unreal,  so  startling  are 
the  tales  that  have  been  told.  We  may  well  im- 
agine the  bravery  that  will  nerve  men  to  fight 
thousands  of  feet  above  the  earth. 

One  of  the  most  thrilling  combats  took  place 
between  a  Russian  aeroplane  and  a  Zeppelin,  over 
Russian  Poland,  at  the  time  of  the  first  German 
invasion.  The  Zeppelin  was  soaring  over  the 
Russian  position,  at  an  altitude  of  about  a  mile. 
A  Russian  aviator  ascended  and  after  circling 
about,  so  as  to  gain  a  position  higher  than  the 
airship,  darted  down,  and  crashed  into  the  great 
gas  field. 

The  aviator  knew  that  it  meant  death  to  him, 
but  his  devotion  led  him  to  make  the  sacrifice. 
The  Zeppelin,  broken  in  two,  and  robbed  of  its 
gas,  slowly  moved  toward  the  earth,  then  gradu- 
ally increased  the  speed  of  its  descent,  as  the 
aeroplane  clung  to  its  shattered  hulk,  and  by  the 


216  AEKOPLANES 

time  it  neared  the  earth  its  velocity  was  great 
enough  to  assure  the  destruction  of  all  on  board, 
while  the  ship  itself  was  crushed  to  atoms. 

One  of  the  most  spectacular  fights  of  the  war 
occurred  outside  Paris,  when  one  of  the  German 
Taubes  attempted  to  make  its  periodical  tour 
of  observation.  One  of  the  French  aeroplanes, 
which  had  the  advantage  of  greater  speed, 
mounted  to  a  greater  altitude,  and  circled  about 
the  Taube. 

The  latter  with  its  machine  gun  made  a  furious 
attack,  during  these  maneuvers,  but  the  French 
ship  did  not  reply  until  it  was  at  such  an  eleva- 
tion that  it  could  deliver  the  attack  from  above. 
Then  its  machine  gun  was  brought  into  play.  As 
was  afterwards  discovered,  the  wings  and  body 
of  the  Taube  were  completely  riddled,  and  it  was 
a  marvel  how  it  was  possible  for  the  German  avia- 
tor to  remain  afloat  as  long  as  he  did. 

Soon  the  Taube  was  noticed  to  lurch  from  side 
to  side,  and  then  dart  downwardly.  The  mono- 
plane, in  the  pursuit,  gradually  descended,  but  it 
was  not  able  to  follow  the  destroyed  Taube  to  the 
earth,  as  the  latter  finally  turned  over,  and  went 
swirling  to  destruction. 

The  observer,  as  well  as  the  aviator,  had  both 
been  killed  by  the  fire  from  the  monoplane. 

In  the  trenches  on  the  Marne,  to  the  northeast 


AEROPLANE  IN  THE  GREAT  WAR     217 

of  Paris,  where  the  most  stubborn  conflict  raged 
for  over  a  week,  the  air  was  never  clear  of  aero- 
planes. They  could  be  seen  in  all  directions,  and 
almost  all  types  of  machines  were  represented. 
The  principal  ones,  however,  were  monoplanes. 

THE  GERMAN  TAUBE. — The  German  Taube  is  a 
monoplane,  its  main  supporting  surfaces,  as  well 
as  the  tail  planes,  are  so  constructed  that  they 
represent  a  bird.  Taube  means  dove.  It  would 
have  been  more  appropriate  to  call  it  a  hawk. 

On  the  other  hand,  the  French  monoplane,  of 
which  the  Bleriot  is  the  best  known  example,  has 
wings  with  well  rounded  extremities,  and  flaring 
tail,  so  that  the  two  can  be  readily  distinguished. 

On  one  occasion,  during  the  lull  in  the  battle, 
two  of  the  Taubes  approached  the  area  above  the 
French  lines,  and  after  ascending  to  a  great 
height,  began  the  volplane  toward  their  own  lines. 
Such  a  maneuver  was  found  to  be  the  most  ad- 
vantageous, as  it  gave  the  scouting  aeroplane  the 
advantage  of  being  able  to  discover  the  positions 
and  movements  with  greater  ease,  and  at  the  same 
time,  in  case  of  accident  to  the  machine,  the  im- 
petus of  the  flight  would  be  to  their  own  lines. 

Three  of  the  French  aeroplanes  at  once  began 
their  circling  flight,  mounting  higher  and  higher, 
but  without  attempting  to  go  near  the  Taubes. 
When  the  French  ( ships  had  gained  the  proper  al- 


218  -AEROPLANES 

titude,  they  closed  in  toward  the  German  ships, 
before  the  latter  could  reach  their  own  lines  in 
their  volplaning  act. 

This  meant  that  they  must  retreat  or  fight,  and 
the  crack  of  the  guns  showed  that  it  meant  a 
struggle.  The  monoplanes  circled  about  with 
incredible  skill,  pouring  forth  shot  after  shot. 
Soon  one  of  the  Taubes  was  seen  to  flutter. 
This  was  the  signal  for  a  more  concentrated  at- 
tack on  her. 

The  army  in  the  trenches,  and  on  the  fields  be- 
low, witnessed  the  novel  combat.  The  flying 
ships  were  now  approaching  the  earth,  but  the 
gunners  below  dared  not  use  their  guns,  because 
in  the  maneuvers  they  would  be  as  likely  to  strike 
friend  as  foe. 

The  wounded  Taube  was  now  shooting  to  the 
earth,  and  the  two  monoplanes  began  to  give  their 
attention  to  the  other  ship,  which  was  attempting 
to  escape  to  the  north.  The  flash  of  the  guns  of 
all  the  fliers  could  be  plainly  seen,  but  the  sounds 
were  drowned  by  the  roar  of  the  great  conflict  all 
about  them. 

The  Taube  could  not  escape  the  net  around  her. 
She,  too,  was  doomed.  A  shot  seemed  to  strike 
the  gasoline  tank,  and  the  framework  was  soon 
enveloped  in  flames.  Then  she  turned  sidewise, 
as  the  material  on  one  side  burned  away,  and  skid- 


AEEOPLANE  IN  THE  GREAT  WAR     219 

ding  to  the  left  she  darted  to  the  earth,  a  shape- 
less mass. 

It  was  found  that  the  aviator  was  not  hurt  by 
the  shot,  but  was,  undoubtedly,  killed  by  the  im- 
pact with  the  earth.  The  observer  was  riddled 
with  bullets,  and  was  likely  dead  before  the  ship 
reached  the  earth. 

In  the  western  confines  of  Belgium,  near  Ypres, 
the  British  employed  numerous  aircraft,  many  of 
them  biplanes,  and  at  all  times  they  were  in  the 
air,  reporting  observations.  Many  of  the  flying 
fights  have  been  recorded,  and  the  reports  when 
published  will  be  most  thrilling  reading. 

How  AEROPLANES  REPORT  OBSERVATIONS. — It 
may  be  of  some  interest  to  know  how  aeroplanes 
are  able  to  report  observations  to  the  command- 
ers in  the  field,  from  the  airship  itself.  Many 
ingenious  devices  have  been  devised  for  this  pur- 
pose. 

SIGNAL  FLAGS. — The  best  known  and  most  uni- 
versally used  method  is  by  the  use  of  signaling 
flags.  Suppose  the  commander  of  a  force  is  de- 
sirous of  getting  the  range  of  a  hidden  battery, 
or  a  massed  force  in  his  front.  The  observer  in 
the  aeroplane  will  sail  over  the  area  at  an  under- 
stood altitude,  say  one  mile  in  height. 

The  officer  in  charge  of  the  battery,  knowing 
the  height  of  the  airship,  is  able,  by  means  of 


220  AEROPLANES 

the  angle  thus  given  him,  to  get  the  distance  be- 
tween his  battery  and  the  concealed  point  beneath 
the  airship.  The  observer  in  the  airship,  of 
course,  signals  the  engineer  officer,  the  exact  point 
or  time  when  the  airship  is  directly  above,  and 
this  gives  him  the  correct  angle. 

The  guns  of  the  battery  are  then  directed  and 
fired  so  as  to  reach  the  concealed  point.  It  is 
now  important  to  be  able  to  send  intelligible  sig- 
nals to  the  officer  in  charge  of  the  battery.  If  the 
shot  goes  beyond  the  mark,  the  observer  in  the 
airship  raises  the  flag  above  his  head,  which  in- 
dicates that  it  was  too  high. 

How  USED. — If  the  shot  fell  short  he  would 
lower  the  flag.  If  the  shot  landed  too  far  to  the 
right,  this  would  be  indicated  by  the  flag,  and  if 
too  far  to  the  left,  the  signal  would,  in  like  man- 
ner, be  sufficient  to  enable  the  gunners  to  correct 
the  guns. 

When  the  exact  range  is  obtained  the  observer 
in  the  ship  waves  the  flag  about  his  head,  in 
token  of  approval.  All  this  work  of  noting  the 
effect  of  the  shots  must  be  taken  while  the  air- 
ship is  under  fire,  and  while  circling  about  within 
visual  range  of  the  concealed  object  below. 

The  officer  in  charge  of  the  battery,  as  well  as 
the  observer  on  the  flying  craft,  must  be  equipped 
with  powerful  glasses,  so  the  effect  of  the  shots 


AEROPLANE  IN  THE  GEEAT  WAR     221 

may  be  noted  on  the  one  hand,  and  the  signals 
properly  read  by  the  officer  on  the  other  hand. 

It  may  be  said,  however,  that  air  battles  have 
not  been  frequent  and  that  they  have  been  merely 
incidents  of  the  conditions  under  which  they  were 
operated.  The  mission  of  the  aeroplane  is  now 
conceded  to  be  purely  one  of  observation,  such  as 
we  have  described. 

Both  French  and  German  reports  are  full  of 
incidents  showing  the  value  of  observations,  and 
also  concerning  the  effects  of  bombs.  Extracts 
from  the  diaries  of  prisoners  gave  many  interest- 
ing features  of  the  results  of  aeroplane  work. 

CASUALTIES  DUE  TO  AEROPLANES. — In  the  diary 
of  one  was  found  the  remark:  "I  was  lucky  to 
escape  the  bomb  thrown  by  a  French  aviator  at 
Conrobet,  which  killed  eight  of  my  companions." 

Another  says:  "The  Seventh  Company  of  the 
Third  Regiment  of  the  Guard  had  eight  killed  and 
twenty-two  wounded  by  bomb  from  a  French  aero- 
plane. '$ 

Another:  "An  officer  showed  us  a  torn  coat 
taken  from  one  of  sixty  soldiers  wounded  by  a 
bomb  from  an  aeroplane." 

A  prisoner  says :  ' '  Near  Neuville  an  aeroplane 
bomb  dropped  on  a  supply  train,  killed  four  men, 
wounded  six,  and  killed  a  considerable  number  of 
horses." 


222  AEKOPLANES 

The  Belgians,  after  their  defeat  and  the  cap- 
ture of  Antwerp,  were  forced  to  the  west  along 
the  coast.  In  some  way  they  learned  that  the 
Kaiser  was  about  to  occupy  a  chateau  near  Dix- 
munde.  Several  aviators  flew  above  the  position 
and  dropped  a  number  of  bombs  on  the  building, 
wrecking  it,  and  it  was  fortunate  for  him  that 
the  Emperor  left  the  building  only  twenty  min- 
utes before,  as  several  of  his  aides  and  soldiers 
on  duty  were  killed. 

On  numerous  occasions  the  headquarters  of  the 
different  commanders  have  been  discovered  and 
had  to  be  moved  to  safer  places. 

During  all  these  wonderful  exploits  which  will 
live  in  history  because  men  had  the  opportunity 
during  the  war  to  use  them  for  the  first  time  in 
actual  conflict,  the  official  reports  have  not  men- 
tioned the  aviators  by  name.  The  deaths  of  the 
brave  men  have  brought  forth  the  acknowledg- 
ments of  their  services.  During  the  first  three 
months  of  the  war  it  is  estimated  that  over  sixty 
aviators  and  aides  had  lost  their  lives  in  the  con- 
flict on  the  two  great  battle  lines.  This  does  not 
take  into  account  those  who  met  death  on  the 
Zeppelins,  of  which  five  had  been  destroyed  dur- 
ing that  time. 

THE  END 


GLOSSARY  OF  WORDS 

USED  IN  TEXT  OF  THIS  VOLUME 

Where  a  word  has  various  meanings,  that  definition  is  given 
which  will  express  the  terms  used  by  the  author  in  explaining 
the  mechanism  or  subject  to  which  it  refers. 

Aviation.  The  art  of  flying. 

Altitude.  Height;  a  vertical  distance  above  any  point. 

Attraction.         The  art  or  process  of  drawing  towards. 

Allusion.  Referring  to  a  certain  thing. 

Assume.  Taking  it  for  granted. 

Accentuated.      To  lay  great  stress  upon  a  thing. 

Angle  of  Any  direction  which  is  upwardly  or  downwardly,  as 

Movement.         distinguished  from  the  direction  of  movement  which 
is  either  to  the  right  or  to  the  left. 

Acquired.  To  obtain;  to  recover;  to  procure. 

Analogous.         Corresponding  to  or  resembling  some  other  thing  or 
object. 

Air  Hole.  A  term  used  to  express  a  condition  in  flying  where 

the  machine  while  in  horizontal  flight  takes  a  sud- 
den drop,  due  to  counter  currents. 

Ailerons.  Literally,  small  planes.     Used  to  designate  the  small 

planes  which  are  designed  to  stabilize  a  machine. 

Angle.  A  figure,  or  two  straight  lines  which  start  at  the 

same  point.    The  sides  of  these  lines  are  termed 
the  angle. 

Analysis.  To  separate;  to  take  apart  and  examine  the  various 

parts  or  elements  of  a  thing. 
223 


224 


GLOSSAEY 


Aeroplane.  Any  form  of  machine  which  has  planes,  and  is  heavier 
than  air.  Usually  a  flying  structure  which  is  pro- 
pelled by  some  motive  power. 

Accumulation.  Adding  to;  bringing  together  the  same  or  unlike 
articles. 

Ascribable.        A  reference  to  some  antecedent  source. 

Aeronautics.      The  science  of  flying. 

Anterior.  Meaning  the  front  or  forward  margin  or  portion  of  a 

body. 

Artifices.  Any  artificial  product,  or  workmanship. 

Axially.  Through  the  central  portion.  Thus,  the  shaft  which 

goes  through  a  cylinder  is  axially  arranged. 

Automatic.  A  thing  which  operates  by  its  own  mechanism;  a 
contrivance  which  is  made  in  such  a  manner  that 
it  will  run  without  manual  operation  or  care. 

Alertness.          Quick;  being  active. 

Apex.  The  point  at  which  two  lines  meet;  also  the  extreme 

pointed  end  of  a  conical  figure. 

Ascension.         Moving  upwardly. 

Accessories.  The  parts  of  a  machine,  or  articles  which  may  be 
used  in  connection  therewith. 

Anemometer.  An  instrument  for  measuring  the  force  or  the  veloc- 
ity of  wind. 

Anemograph.  An  instrument  that  usually  traces  a  curved  line  on 
paper  to  make  a  record  of  the  force  or  direction, 
or  velocity  of  the  wind. 

Anemometro-  A  device  which  determines  the  force,  velocity  and 
graph.  direction  of  the  wind. 

Accretion.          Adding  to  little  by  little. 

Accelerated.       Quickening;  hurrying  the  process. 

Abridged.  Partly  taken  away  from;  shortened. 

Abrogate.  To  dispense  with;  to  set  aside. 


GLOSSARY 


225 


Abnormal.          Not  in  the  usual  manner;  not  in  a  regular  way. 

Alternate.  First  one  and  then  another;  going  from 'one  side  to 

the  other. 

Ancient  An  old  English  law  which  prevents  a  neighbor  from 

Lights.  shutting  off  sunlight. 

Angularly.         A  line  which  runs  out  from  another  so  that  the  two 
are  not  parallel. 

Aneroid.  Not  wet.     Applied  to  the  type  of  barometer  where 

the  medium  for  determining  the  pressure  is  not 
made  of  mercury. 

Aspirate.  A  term  given  by  the  French  to  that  peculiar  action 

of  wing,  or  other  body,  which,  when  placed  in  cer- 
tain positions,  relative  to  a  current  of  air,  will 
cause  it  to  be  drawn  into  the  current. 

Assemblage.       The  bringing  together  of  the  parts  or  elements  of  a 
machine. 

Augment.  To  aid;  to  add  to  or  increase. 

Banked.  The  term  used  in  aviation  which  indicates  that  the 

machine  is  turned  up  so  that  its  supporting  sur- 
faces rest  against  the  air,  as  in  alighting. 

Barometer.         An  instrument  for  determining  the  air  pressure,  and 
thereby  indicating  altitudes. 

Bevel  Pinion.     A  toothed  wheel  driven  by  a  larger  wheel. 

Bi-Plane.  Two  planes.     In  aviation  that  type  which  has  two 

planes,  similar  in  size,  usually,  and  generally 
placed  one  above  the  other  so  they  are  separated 
the  same  distance  from  each  other,  as  the  width  of 
each  of  the  planes. 

Bulges.  A  hump;  an  enlargement  beyond  the  normal  at  any 

point. 

Camber,  also     The  upward  curve  in  a  plane. 
Cambre. 


226 


GLOSSAEY 


Catapult.  A  piece  of  mechanism  for  projecting  or  throwing  a 

missile. 
Carbureter.        The  device  which  breaks  up  the  fuel  oil,  and  mixes 

the  proper  quantity   of   air  with   it  before  it  is 

drawn  into  the  engine. 

Catastrophe.       A  calamity;  a  sad  ending;  loss  of  life  or  of  property. 
Cellular.  Made  up  of  small  hollows,  or  compartments ;   filled 

with  holes. 

Celestial.  Pertaining  to  the  heavens. 

Centrifugal.       That  force  which  throws  outwardly  from  a  rotating 

body. 
Centripetal.       That   force,   like   the   attraction   of   gravity,   which 

draws  a  body  to  the  center. 
Character-         Striking;   that  which  is  peculiar  to  some  thing  or 

istic.  object. 

Commen-  Sufficient;    in  proper  proportion;    sufficient  for  the 

surate.  occasion. 

Commercially.  Pertaining  to  the  nature  of  trade;   the  making  of 

money. 

Complicated.      Not  easily  explainable;  not  easy  to  separate. 
Compara-  Judged  by  something  else;   taken  with  reference  to 

tively.  another  object  or  thing. 

Compression.      The  drawing  together;   forcing  into  a  smaller  com- 
pass, or  space. 

Composition.      Made  up  of  different  elements,  or  things. 
Conceivable.       Made  up  from  the  imagination. 
Concaved.  Hollowed:  In  aviation  it  has  reference  to  the  under 

side  of  the  plane,  which  is  usually  provided,  struc- 

turally,  with  a  hollow  or  trough  formation. 

Conforming.       To  make  alike  in  form;  to  bring  into  harmony. 
Conjunction.      In  connection  with;   joining  together. 
Convex.  A  rounded  surface;  a  bulging  out. 


GLOSSARY 


227 


Conclusion.  The  end;  a  finding  in  law;  a  reasoning  from  a  cer- 
tain condition. 

Conductivity.  The  property  of  materials  whereby  they  will  trans- 
mit heat  along  from  one  part  to  another,  also 
electricity. 

Concentrated.    Brought  together;  assembled  in  a  smaller  space. 

Conclusive.        A  positive  ending;  decisive  of  the  matter  at  issue. 

Concentri-          A  line  which  is  at  all  points  at  the  same  distance 
cally.  from  one  point. 

Condensation.  The  act  or  process  of  making  denser,  or  being 
brought  together. 

Contemplate.      To  consider;  to  judge. 

Convoys.  A  protecting  force  which  accompanies  the  transfer 

of  property. 

Convection.        The  diffusion  of  heat  through  a  liquid  or  gas. 

Consistent.         A  state  of  harmony;  the  same  at  all  times. 

Constant.  In  mathematics,  a  figure  which  never  changes;  or  a 

figure  used  as  a.  fixed  valuation  in  a  problem. 

Controllable.  Held  within  bounds;  that  which  can  be  within  the 
power  to  accomplish. 

Correctional.      The  means  whereby  a  fault  may  be  made  right. 

Consequence.     The  result;  that  which  flows  from  a  preceding  action. 

Counterforce.    An  action  contrary  or  opposite  to  the  main  force. 

Counter-  Any  power  equally  opposing  another, 

balance. 

Counteract.        A  force  acting  in  opposition  to  another. 

Counter  An  air  current  which  sets  up  in  an  opposite  direc- 

current.  tion  in  the  path  of  a  moving  aeroplane. 

Cushioned.  An  action  which  takes  place  against  a  moving  aero- 
plane, by  a  sudden  gust  of  air  or  countercurrent. 

Dedicated.          To  set  apart  for  some  special  purpose. 

Degree.  An  interval;  a  grade;  a  stage;  a  certain  proportion. 


228 


GLOSSARY 


Deltoid.  Shaped  like  the  Greek  letter  delta. 

Density.  Closeness  of  parts. 

Demonstra-  Making  clear;  showing  up;  an  exhibition  or  ex- 
tion.  pression. 

Deceptive.  The  power  or  tendency  to  give  a  false  impression. 

Deterrent.  To  hold  back;  to  prevent  action. 

Detracting.  The  tendency  to  take  away;  to  belittle. 

Depressed.  To  move  downwardly. 

Destination.  The  place  set  for  the  end  of  the  journey. 

Despoiling.  To  take  away  from;  robbing  or  taking  from  another 
by  force  or  by  stealth. 

Dependant.  Hanging  below;  projecting  from  the  lower  side. 

Dexterity.  Agility;  smartness  in  action. 

Deranged.  Put  out  of  order;  wrongly  arranged. 

Develop.  Brought  out;  to  put  into  a  correct  shape  or  form. 

Deferred.  Put  over  to  another  time. 

Designedly.  With  a  direct  purpose. 

Diagonal.  Across  an  object  at  an  angle  to  one  or  more  sides. 

Diametri-  Across  an  object  through  or  near  the  center  thereof, 
cally.  . 

Diagram.  A  mechanical  plan  or  outline  of  an  object. 

Dimension.  The  distance  across  an  object.  The  measurement, 
for  instance,  of  a  propeller  from  tip  to  tip. 

Dynamically.  Pertaining  to  motion  as  a  result  of  force. 

Dispossessed.  A  term  used  to  indicate  the  act  which  removes  a 
person  from  the  possession  of  property. 

Diameter.  The  measurement  across  an  object. 

Divest.  Taken  away  from;  removed  out  of. 

Disregard.  Deliberate  lack  of  attention. 

Diversity.  The  state  wherein  one  is  unlike  another;  dissimi- 
larity. 


GLOSSARY 


229 


Drift.  The  term  used  to  indicate  the  horizontal  motion,  or 

the  pull  of  an  aeroplane. 

Dragon.  A  fabulous  monster,  usually  in  the  form  of  a  ser- 

pent. 

Duplicate.  Two;  made  in  exact  imitation  of  an  original. 

Easement.  A  legal  phrase  to  designate  that  right  which  man 
possesses,  irrespective  of  any  law,  to  gain  access 
to  his  property. 

Effrontery.         Boldness  with  insolence;  rashness  without  propriety. 

Effective.  To  be  efficient. 

Element.  One  part  of  a  whole. 

Elasticity.  Material  which  will  go  back  to  its  original  form 
after  being  distorted,  is  said  to  be  elastic. 

Eliminate.          To  take  away  from;  to  remove  a  part,  or  the  whole. 

Elliptical.  Oblong  with  rounded  ends. 

Elusive.  Capable  of  escaping  from;  hard  to  hold. 

Elevator.  The  horizontal  planes  in  front  or  rear,  or  in  both 

front  and  rear  of  the  supporting  surfaces  of  an 
aeroplane. 

Emergency.        A  sudden  occurrence  calling  for  immediate  action. 

Emplacement.  A  spot  designed  to  hold  heavy  field  pieces  in  in- 
trenchments. 

Enactment.  The  formulation  of  a  law;  the  doing  of  a  special 
thing. 

Enunciated.       Announced;  setting  forth  of  an  act  or  a  condition. 

Energy.  That  quality  by  reason  of  which  anything  tends  to 

move  or  act. 

Equidistant.  Two  points  or  objects  at  equal  distance  from  a  com- 
mon point. 

Equilibrium.  A  balance  produced  by  the  action  of  two  or  more 
forces. 


230 


GLOSSARY, 


Equalizing.        One  made  equal  to  the  other;  one  side  the  same  as 

the  other. 
Equipped.  Armed ;  provided  with  the  proper  material,  or  in  the 

same  condition. 

Essential.  The  important  part  or  element. 

Essence.  The  real  character  or  element  of  the  thing  itself. 

External.  The  outermost  portion. 

Evolution.          A  gradual  change  or  building  up;  from  a  lower  to 

a  higher  order. 

Evolved.  Brought  out  from  a  crude  condition  to  a  better  form. 

Expression.        The  art  of  explaining  or  setting  forth. 
Expansion.         Growing  larger;  to  occupy  a  greater  spa.ce. 
Exerted.  To  work  to  the  utmost;  to  put  forth  in  action. 

Exhilaration.     A  lively,  pleasing  or  happy  sensation. 
Exploited.  To  fully  examine  and  consider,  as  well  as  carry  out. 

Extremity.         The  end;  as  far  as  can  be  considered. 
Facility.  Ease   of   management;    to    do   things    without    diffi- 

culty. 
Factor.  One  of  the  elements  in  a  problem,  or  in  mechanical 

action. 

Fascination.       Attractiveness  that  is  pleasing. 
Flexure.  The  capacity  to  bend  and  yield,  and  return  to  its 

original  position. 

Flexible.  That  which  will  yield;  springy. 

Fore  and  Aft.     Lengthwise,  as  from  stem  to  stern  of  a  ship. 
Formation.         The  shape  or  arrangement  of  an  article  or  thing. 
Formulated.       Put  into  some  concrete  form,  or  so  arranged  that  it 

may  be  understood. 

Frictionless.      Being  without  a  grinding  or  retarding  action. 
Fulcrumed.        A  resting  place  for  a  lever. 
Function.  The  duty  or  sphere  of  action  in  a  person,  or  object. 


GLOSSARY 


231 


Glider.  An  aeroplane,  without  power,  adapted  to  be  operated 

by  an  aviator. 

Governing.  An  element  which  is  designed  to  control  a  machine  in 
a  regular  manner. 

Graduated.  A  marked  portion,  which  is  regularly  laid  off  to  in- 
dicate measurements  or  quantities. 

Gravity.  The  attraction  of  mass  for  mass.  The  tendency  of 

bodies  to  move  toward  the  earth. 

Gravitation.       The  force  with  which  all  bodies  attract  each  other. 

Gyratory.  Having  a  circular  and  wheeling  as  well  as  a  rotary 

motion. 

Gyroscope.  A  wheel,  designed  to  illustrate  the  laws  of  motion, 
which  freely  revolves  in  gimbals  within  a  ring, 
and  when  set  into  motion,  objects  to  change  its 
plane  of  rotation. 

Hemispher-  The  half  of  a  sphere.  The  half  of  an  apple  would 
ical.  be  hemispherical. 

Hazardous.         That  which  is  doubtful;   accompanied  by  danger. 

Helicopter.  A  type  of  flying  machine  which  has  a  large  pro- 
peller, or  more  than  one,  revolubly  fixed  on  ver- 
tical shafts,  by  means  of  which  the  machine  is 
launched  and  projected  through  the  air. 

Horizontal.        Level,  like  water. 

Hydroplane.  A  term  used  to  designate  an  aeroplane  which  is 
provided  with  pontoons,  whereby  it  may  alight  on 
the  water,  and  be  launched  from  the  surface.  The 
term  Hydroaeroplane  is  most  generally  used  to 
indicate  this  type  of  machine. 

Impact.  The  striking  against;  the  striking  force  of  one  body 

against  another. 

Immersed.          Placed  under  water  below  the  surface. 


232 


GLOSSABY, 


Impinge.  To  strike  against;  usually  applied  where  air  strikes 

a  plane  or  a  surface  at  an  angle. 

Imitation.          Similarity;  the  same  in  appearance. 

Incompatible:    Without  harmony;  incapable  of  existing  together. 

Incurved.  Applied  to  a  surface  formation  where  there  is  a  de- 

pression, or  hollow. 

Inequalities.      Not  smooth,  or  regular;  uneven. 

Infinitely.  Boundless;  in  great  number,  or  quality;  without 
measure. 

Initial.  The  first;  that  which  is  at  the  beginning. 

Indestruct-        Not  capable  of  being  injured  or  destroyed, 
ibility. 

Influenced.         Swayed;  to  be  induced  to  change. 

Inherent.  That  which  is  in  or  belongs  to  itself. 

Initiating1.         To  teach;  to  instill;  to  give  an  insight. 

Indicator.  A  term  applied  to  mechanism  which  shows  the  re- 

sults of  certain  operations  and  enables  the  user  to 
read  the  measure,  quantity,  or  quality  shown. 

Inconceiv-         Not  capable  of  understanding;  that  which  cannot  be 
able.  understood  by  the  human  mind. 

Institute.  To  start;  to  bring  into  operation. 

Insignias.  Things  which  are  significant  of  any  particular  call- 

ing or  profession. 

Instinct.  That  quality  in  man  or  animals  which  prompts  the 

doing    of    things    independently    of    any    direct 
knowledge  or  undestanding. 

Intermediate.  Between;  that  which  may  be  within  or  inside  the 
scope  of  the  mind,  or  of  certain  areas. 

Intervening.  The  time  between;  also  applied  to  the  action  of  a 
person  who  may  take  part  in  an  affair  between  two 
or  more  persons. 

Interval.  A  time  between. 


GLOSSARY 


233 


Investigator. 
Incidence. 

Inverted. 
Invest. 

Kinetic. 
Laminated. 


launching. 
Lateral. 


Lift. 


Ligament. 

Limitations. 
Longitud- 
inally. 
Majestically. 

Manipulate. 


One  who  undertakes  to  find  out  certain  things. 

In  physics  this  is  a  term  to  indicate  the  line  which 
falls  upon  or  strikes  another  at  an  angle. 

Upside  down. 

To  give  to  another  thing  something  that  it  lacked 
before. 

Consisting  in  or  depending  upon  motion. 

Made  up  of  a  plurality  of  parts.  When  wooden 
strips,  of  different  or  of  the  same  kinds  are  glued 
and  then  laid  together  and  put  under  heavy  pres- 
sure until  thoroughly  dried,  the  mass  makes  a 
far  more  rigid  structure  than  if  cut  out  of  a 
single  piece. 

The  term  applied  to  the  raising,  or  starting  of  a 
boat,  or  of  a  flying  object. 

In  mining  this  is  a  term  to  indicate  the  drifts  or 
tunnels  which  branch  out  from)  the  main  tunnel. 
Generally  it  has  reference  to  a  transverse  position 
or  direction, — that  is,  at  right  angles  to  a  fore 
and  aft  direction. 

The  vertical  motion,  or  direction  in  an  airship;  thus 
the  lift  may  be  the  load,  or  the  term  used  to  desig- 
nate what  the  ship  is  capable  of  raising  up. 

The  exceedingly  strong  tendons  or  muscles  of  birds 
and  animals,  usually  of  firm,  compact  tissues. 

Within  certain  bounds;   in  a  prescribed  scope. 

Usually  that  direction  across  the  longest  part. 

Grand;   exalted  dignity;  the  quality  which  inspires 

reverence  or  fear. 
To  handle;   to  conduct  so  that  it  will  result  in  a 

certain  way. 


234 


GLOSSARY 


Maneuver.         A  methodical  movement  or  change  in  troops. 

Manually.          To  perform  by  hand. 

Manifesta-  The  act  of  making  plain  to  the  eye  or  to  the  under- 
tlons.  standing. 

Manually-  With  the  hands;  a  term  applied  to  such  machines  as 
operated.  have  the  control  planes  operated  by  hand. 

Maintained.       Kept  up;  to  provide  for;  to  sustain. 

Material.  The  substance,  or  the  matter  from  which  an  article 

is  made;  also  the  important  thing,  or  element. 

Mass.  In  physics  it  is  that  which  in  an  article  is  always 

the  same.  It  differs  from  weight  in  the  particular 
that  the  mass  of  an  article  is  the  same,  however 
far  it  may  be  from  the  center  of  the  earth,  whereas 
weight  changes,  and  becomes  less  and  less  as  it 
recedes  from  the  center  of  the  earth. 

Margin.  The  edge;  the  principal  difference  between  this  word 

and  edge,  is,  that  margin  has  reference  also  to  a 
border,  or  narrow  strip  along  the  edge,  as,  for  in- 
stance, the  blank  spaces  at  the  edges  of  a  printed 
page. 

Medieval.  Belonging  to  the  Middle  Ages. 

Mercury.  A  silver-white  liquid  metal,  usually  called  quicksil- 

ver, and  rather  heavy.  It  dissolves  most  metals, 
and  this  process  is  called  amalgamation. 

Militate.  In  determining  a  question,  to  have  weight,  or  to 

influence  a  decision. 

Mobility.  Being  freely  movable;  capable  of  quick  change. 

Modification.     A  change;  making  a  difference. 

Monitor.  Advising  or  reproving.  Advising  or  approving  by 

way  of  caution. 

Monstrosi-  Anything  which  is  huge,  or  distorted,  or  wrong  in 
ties.  structure. 


GLOSSARY 


235 


Monorail.  A  railway  with  a  single  track,  designed  to  be  used 

by  a  bicycle  form  of  carriage,  with  two  wheels, 
fore  and  aft  of  each  other,  and  depending  for  its 
stability  upon  gyroscopes,  mounted  on  the  car- 
riage. 

Momentum.  That  which  makes  a  moving  body  difficult  to  stop. 
It  is  the  weight  of  a  moving  body,  multiplied  by 
its  speed. 

Monoplane.  The  literal  meaning  is  one  plane.  As  monoplane 
machines  are  all  provided  with  a  fore  and  aft 
body,  and  each  has  a  wing  or  plane  projecting  out 
from  each  side  of  this  body,  it  is  obvious  that  it 
has  two  planes  instead  of  one.  The  term,  how- 
ever, has  reference  to  the  fact  that  it  has  only 
one  supporting  surface  on  the  same  plane.  Bi- 
planes have  two  supporting  surfaces,  one  above  the 
other. 

Multiplicity.  Frequently  confounded  with  plurality.  The  latter 
means  more  than  one,  whereas  multiplicity  has 
reference  to  a  great  number,  or  to  a  great  variety. 

Muscular.  Being  strong;  well  developed. 

Negative.  The  opposite  of  positive;  not  decisive. 

Neutralize.  From  the  word  neuter,  which  means  neither,  hence 
the  termi  may  be  defined  as  one  which  is  not  a 
part  of  either,  or  does  not  take  up  with  either  side. 

Normal  Pres-  Normal  means  the  natural  or  usual,  and  when  ap- 
sure.  plied  to  air  it  would  have  reference  to  the  condi- 

tion of  the  atmosphere  at  that  particular  place. 
If  the  pressure  could  change  from  its  usual  con- 
dition, it  would  be  an  abnormal  pressure. 

Notoriously.  Generally  known,  but  not  favorably  so;  the  subject 
of  general  remark;  or  unfavorably  known. 


236 


GLOSSAEY 


Obscurity.  Not  well  known;  in  the  background;  without  cleat 
vision;  hidden  from  view. 

Obliquely.  That  which  differs  from  a  right  angle;  neither 
obtuse  nor  acute;  deviating  from  a  line  by  any 
angle  except  a  right  angle. 

Obvious.  That  which  is  readily  observed  and  understood. 

Orthopter.  That  type  of  flying  machine  which  depends  on  flap- 
ping wings  to  hold  it  in  space,  and  to  transport 
it,  in  imitation  of  the  motion  of  the  wings  of 
birds  in  flying. 

Oscillate.  Moving  to  and  fro;  the  piston  of  a  steam  engine  has 

an  oscillating  motion. 

Outlined.  Describing  a  marginal  line  on  a  drawing;  setting 

forth  the  principal  features  of  an  argument,  or 
the  details  of  a  story,  or  the  like. 

Overlapping.      One  placed  over  the  other. 

Parabolic.          A  form  of  curve  somewhat  similar  to  an  ellipse. 

Pedestal.  A  standard  or  support;  an  upright  to  hold  ma- 

chinery. 

Pertinent.          Appropriate;   pertaining  to  the  subject. 

Pectoral.  The  bone  which  forms  the  main  rib  or  support  at  the 

forward  edge  of  a  bird's  wing. 

Persistent.         Keeping  at  it;  determination  to  proceed. 

Perpendic-  lAt  right  angles  to  a  surface.  This  term  is  some- 
ular.  times  wrongly  applied  in  referring  to  an  object, 

particularly  to  an  object  which  is  vertical,  mean- 
ing up  and  down.  The  blade  of  a  square  is  per- 
pendicular to  the  handle  at  all  times,  but  the 
blade  is  vertical  only  when  it  points  to  the  center 
of  the  earth. 

Pernicious.  Bad;  not  having  good  features  or  possessing  wrong 
attributes. 


GLOSSAEY 


237 


Pendulum.  A  bar  or  body  suspended  at  a  point  and  adapted  to 
swing  to  and  fro. 

Perpetuity.         For  all  time;  unending  or  unlimited  time. 

Phenomena.       Some  peculiar  happening,  or  event,  or  object. 

Pitch.  In  aviation  this  applies  to  the  angle  at  which  the 

blades  of  a  propeller  are  cut.  If  a  propeller  is 
turned,  and  it  moves  forwardly  in  the  exact  path 
made  by  the  angle,  for  one  complete  turn,  the 
distance  traveled  by  the  propeller  axially  indi- 
cates the  pitch  in  feet. 

Placement.  When  an  object  is  located  at  any  particular  point, 
so  that  it  is  operative  the  location  is  called  the 
placement. 

Plane.  A  flat  surface  for  supporting  a  flying  machine  in 

the  air.  Plane  of  movement  pertains  to  the  imag- 
inary surface  described  by  a  moving  body.  A  bi- 
cycle wheel,  for  instance,  when  moving  forwardly 
in  a  straight  line,  has  a  plane  of  movement  which 
is  vertical;  but  when  the  machine  turns  in  a 
circle  the  tipper  end  of  the  wheel  is  turned  in- 
wardly, and  the  plane  of  movement  is  at  an  angle. 

Pliant.  Easily  yielding;  capable  of  being  bent;  liable  to  be 

put  out  of  shape. 

Plurality.  See  multiplicity.    More  than  ona 

Poise.  Held  in  suspension;  disposed  in  a  particular  way. 

Pontoon.  Applied  to  a  series  of  boats  ranged  side  by  side  to 

support  a  walk  laid  thereon.  In  aviation  it  has 
reference  to  a  float  for  supporting  an  aeroplane. 

Ponderous.         Large;  heavy;  difficult  to  handle. 

Posterior.  The  rear  end;  the  opposite  of  anterior. 

Principles.  The  very  nature  or  essence  of  a  thing;  the  source 
or  cause  from  which  a  thing  springs. 


238  GLOSSARY 

Proportion.  The  relation  that  exists  between  different  parts  or 
things. 

Propounded.  Questioned;  stated;  to  state  formally  for  considera- 
tion. 

Proprietary.      A  right;  the  ownership  of  certain  property. 

Primitive.          The  beginning  or  early  times ;  long  ago. 

Prelude.  A  statement  or  action  which  precedes  the  main  fea- 

ture to  be  presented. 

Proximity.         Close  to;  near  at  hand. 

Prototype.  That  which  is  used  as  the*  .sample  fronn  which  some- 
thing is  made  or  judged. 

Propeller.  The  piece  of  mechanism,  with  screw-shaped  blade, 

designed  to  be  rapidly  rotated  in  order  to  drive 
a  vessel  forwardly.  It  is  claimed  by  some  that 
the  word  Impeller  would  be  the  more  proper 
term. 

Primarily.          At  the  first;  the  commencement. 

Precedes.  Goes  ahead;  forward  of  all. 

Propulsive.         The  force  which  gives  motion  to  an  object. 

Projected.  Thrown  forward;  caused  to  fly  through  the  air. 

Radially.  Out  from  the  center;  projecting  like  the  spokes  of 

a  wheel. 

Ratio.  The  relation  of  degree,  number,  amount;  one  with 

another. 

Reaction.  A  counterforce;  acting  against. 

Recognize.  To  know;  seeing,  hearing,  or  feeling,  and  having 
knowledge  therefrom. 

Reflection.  Considering;  judging  one  thing  by  the  examination 
of  another.  A  beam  of  light,  or  an  object,  leav- 
ing a  surface. 

Refraction.  That  peculiarity  in  a  beam  of  light,  which,  in  pass- 
ing through  water  at  an  angle,  bends  out  of  its 


GLOSSARY 


239 


course  and  again  assumes  a  direct  line  after  pass- 
ing through. 

Reflex.  Turned  back  on  itself,  or  in  the  direction  from  which 

it  came. 

Requisite.          Enough;  sufficient  for  all  purposes. 

Relegate.  To  put  back  or  away. 

Rectangular.     Having  one  or  more  right  angles. 

Reservations.  Land  which  is  held  by  the  Government  for  various 
purposes. 

Resistance.        That  which  holds  back;  preventing  movement. 

Retarding.         Preventing  a  free  movement. 

Revoluble.  The  turning  or  swinging  motion  of  a  body  like  the 
earth  in  its  movement  around  the  sun.  See  Rota- 
tive. To  cause  to  move  as  in  an  orbit  or  circle. 

Resilient.  Springy;  having  the  quality  of  elasticity. 

Reversed.  Changed  about;  turned  front  side  to  the  rear. 

Rotative.  That  which  turns,  like  a  shaft.  The  movement  of 

the  earth  on  its  axis  is  rotative. 

Saturation.  Putting  one  substance  into  another  until  it  will 
hold  no  more.  For  instance,  adding  salt  to  water 
until  the  water  cannot  take  up  any  more. 

Security.  Safety,  assuredness  that  there  will  be  no  danger. 

Segment.  A  part  cut  off  from  a  circle.  Distinguished  from  a 

Sector,  which  might  be  likened  to  the  form  of  one 
of  the  sections  of  an  orange. 

Sexagonal.         Six-sided. 

Sine  of  the  The  line  dropped  from  the  highest  point  of  an 
Angle.  angle  to  the  line  which  runs  out  horizontally. 

Sinuous.  Wavelike;  moving  up  and  down  like  the  waves  of 

the  ocean. 

Simulates.          To  pattern  or  copy  after;  the  making  of  the  like. 

Skipper.  A  thin  flat  stone. 


240 


GLOSSAEY 


Spirally-  Made  like  an  auger;  twisted. 

formed. 

Stability.  In  airships  that  quality  which  holds  the  ship  on  an 

even  and  unswerving  course,  and  prevents  plung- 
ing and  side  motions. 

Structural.         Belonging  to  the  features  of  construction. 

Strata.  Two  or  more  layers;  one  over  or  below  the  other. 

Stream  Line.  In  expressing  the  action  of  moving  air,  or  an  aero- 
plane transported  through  air,  every  part  is  acted 
upon  by  the  air.  Stream  lines  are  imaginary 
lines  which  act  upon  the  planes  at  all  points,  and 
all  in  the  same  direction,  or  angle. 

Stupendous.       Great;  important;  above  the  ordinary. 

Substitute.  One  taken  for  another;  replacing  one  thing  by  some- 
thing else. 

Supporting.       Giving  aid;  helping  another. 

Synchronous.  Acting  at  the  same  time,  and  to  the  same  extent. 
Thus  if  two  wheels,  separated  from  each  other  at 
great  distances,  are  so  arranged  that  they  turn  at 
exactly  the  same  speed,  they  are  said  to  turn  syn- 
chronously. 

Tactics.  The  art  of  handling  troops  in  the  presence  of  an 

enemy.  It  differs  from  strategy  in  the  particular 
that  the  latter  word  is  used  to  explain  the  move- 
ments or  arrangement  of  forces  before  they  arrive 
at  the  battle  line. 

Tandem.  One  before  the  other;  one  after  the  other. 

Tangent.  A  line  drawn  from  a  circle  at  an  angle,  instead  of 

radially. 

Technically.       Pertaining  to  some  particular  trade,  science  or  art. 

Tenuous.  Thin,  slender,  willowy,  slight. 

Tetrahedral.      This  has  reference  to  a  form  which  is  made  up  of  a 


GLOSSARY 


241 


multiplicity  of  triangularly  shaped  thin  blades,  so 
as  to  form  numerous  cells,  and  thus  make  a  large 
number  of  supporting  surfaces.  Used  as  a  kite. 

Theories.  Views  based  upon  certain  consideration. 

Theoretical.  Where  opinions  are  founded  on  certain  information, 
and  expressed,  not  from  the  standpoint  of  actual 
knowledge,  but  upon  conclusions  derived  from 
such  examinations. 

Torsion.  A  twist;  a  circular  motion  around  a  body. 

Transmitted.      Sent  out;  conveyed  from  one  point  to  another. 

Transforma-  Changed;  entirely  made  over  from  one  thing  to 
tion.  another. 

Transverse.  When  a  body  is  shorter  from  front  to  rear  than 
from  side  to  side  its  longest  dimension  is  trans- 
versely. Distinguish  from  lateral,  which  has 
reference  only  to  the  distance  at  right  angles  from 
the  main  body. 

Translation.       The  transportation  of  a  body  through  the  air. 

Trajectory.         The  path  made  by  a  body  projected  through  the  air. 

Triangular.        A  form  or  body  having  three  sides  and  three  angles. 

Typical.  In  the  form  of;  a  likeness  to. 

Ultimate.  The  end;  the  finality;  the  last  that  can  be  said. 

Uninitiated.       Not  having  full  knowledge;   withont  information. 

Unique.  Peculiar;  something  that  on  account  of  its  peculiar 

construction  or  arrangements  stands  out  beyond 
the  others. 

Universal.          Everywhere;  all  over  the  world. 

Undulate.  To  move  up  and  down;  a  wave-like  motion. 

Utility.  Of  use;  to  take  advantageous  use  of. 

Unstable.  Not  having  anything  permanent;  in  a  ship  in  flight 

one  that  will  not  ride  on  an  even  keel,  and  is 
liable  to  pitch  about. 


242 


GLOSSAEY 


Vacuum.  Where  air  is  partly  taken  away,  or  rendered  rarer. 

Valved.  A  surface  which  has  a  multiplicity  of  openings  with 

valves  therein,  or,  through  which  air  can  move  in 

one  direction. 

Vaunted.  To  boast  concerning;  to  give  a  high  opinion. 

Velocity.  Speed;  the  rate  at  which  an  object  can  move  from 

place  to  place. 
Vertically.         A  line  running  directly  to  the  center  of  the  earth ;  a 

line  at  right  angles  to  the  surface  of  water. 
Vibratory.          Moving  from  side  to  side;  a  regular  motion. 
Volplane.  The  glide  of  a  machine  without  the  use  of  power. 

Warping.  The  twist  given  to  certain  portions  of  planes,  so  as 

to  cause  the  air  to  act  against  the  warped  por- 
tions. 
Weight.  The  measure  of  the  force  which  gravity  exerts  on 

all  objects. 


T  L 

5-  V  7 


THE  LIBRARY 
UNIVERSITY  OF  CALIFORNIA 

Santa  Barbara 


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